Psychology Laughter
by
Jennifer Hofmann, Willibald Ruch
  • LAST MODIFIED: 27 April 2017
  • DOI: 10.1093/obo/9780199828340-0189

Introduction

Laughter is an audio-visual expressive-communicative signal, consisting of an initial forced exhalation, followed by a more or less sustained sequence of repeated expirations of high frequency and low amplitude, which may or may not be phonated as “ha-ha-ha.” Different inter-depending systems (respiration, facial action, acoustics, and body movements) are involved in the generation of the expressive pattern. Although it has been claimed that laughter is one of the most important nonverbal human interaction signals, comparatively little psychological work has addressed it directly. Still, research is steadily increasing and developing in various fields, in particular in psychology, medical science, linguistics, and more recently in technical domains (such as affective computing), to name a few. Also, laughter has been claimed to have physiological and psychological benefits of which only some have been substantiated with methodologically sound studies. Laughter is found in humans, as well as other species (some primates and rats; laughter is also acquired by other species when domesticated). Phylogenetically, laughter developed before speech and is supposedly of different origins than smiling. In humans, laughter is an important signal with social functions (i.e., facilitating social relationships), as well as emotion-expressive functions (being a nonverbal marker of joy). It is an innate behavior that typically shows around the fourth month in human infant development. Laughter is often elicited by emotions, and “amusement laughter” is the laughter type most widely researched. Early works often fail to make the distinction between laughter and humor, or use the terms interchangeably. Yet, humor may occur without laughter and vice versa, though mirth is a potent elicitor of laughter. Other emotions go along with laughter as well (i.e., relief, embarrassment). Furthermore, laughter also occurs in non-emotional states (i.e., pathological laughter or due to laughing gas). When studying the morphology of laughter, most works have focused on one modality: either face, voice, or body. In brief, the facial features of laughter typically entail the Duchenne markers (simultaneous and symmetric contraction of the zygomatic major muscle pulling the lip corners up and backward, as well as the orbicularis oculi pars orbitalis muscle, lifting the cheeks), an open mouth/lowered jaw. The involvement of further facial actions has been claimed but rarely tested beyond posed expressions. The laughter vocalization is marked by typical, recognizable patterns that go with specific emotional responses in the listener. For the laughter vocalizations, most results focused on the changes in F0, rhythm, intensity, and voicing. Also, some studies investigated laughter respiration and the bodily involvement (for example the H-reflex, the role of shoulder movements in laughter detection, etc.). Overall, the early-21st-century state of research still faces the challenge of a lack of laughter classifications, a need to determine how many morphologically different laughter types can be distinguished, and an agreement on laughter’s different functions.

General Overviews, Reference Works, and Textbooks

There are no reference works or textbooks on laughter. Interdisciplinary reference works exist for the subject of humor (see Oxford Bibliographies article Humor) and what makes us laugh, but it has been stressed that the two phenomena need to be distinguished: both can occur together, as well as separately. Chapman and Foot 1976 states: “A distinction can—and indeed should—be drawn between theories of humor and theories of laughter, and clearly theories of laughter need to take into account the numerous types of non-humorous, as well as humorous situations which can cause laughter” (p. 4). Provine 2001 states, “The most readily apparent feature of this theorizing is that most of it is really about humor or comedy (i.e., material that stimulates laughter), not laughter itself.” (p. 18). Therefore, while many interesting writings on laughter are situated within humor research, laughter can also occur without humor. In general, interesting accounts on laughter can be found in Darwin 1872 and his coevals (e.g., Gregory 2013, Raulin 1900). Also, Ekman and Rosenberg 2005 contains four chapters on laughter and its occurrence (authored by Eva Bänninger-Huber, Dacher Keltner, and Willibald Ruch). Glenn 2003 is a book on laughter in interaction, looking at laughter from a conversation analysis perspective. Furthermore, some review articles have summarized pertinent issues within the research on laughter: regarding the morphology, Ruch and Ekman 2001 (cited under Morphology of Laughter) describes the morphological features of laughter in detail. Regarding neural correlates, Wild, et al. 2003 summarizes the findings on brain activations during laughter (and humor). Regarding positive health outcomes, Martin 2001 is a broad review on the knowledge on humor, health, and laughter. Moreover, several relevant entries on laughter can be found in the recently published Attardo 2014, which includes four entries relating to laughter (by Goh Abe, Michael J. Owren, Wallace Chafe, and Sven Svebak). Devereux and Heffner 2007 provides an overview on research on laughter from a positive psychological viewpoint, highlighting psychophysiological approaches to laughter research and stressing the role to health and well-being.

  • Attardo, Salvatore, ed. 2014. Encyclopedia of humor research. London: SAGE.

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    Interdisciplinary encyclopedia for humor and laughter scholars and students. Suitable for undergraduate students, too. Of particular interest are the entries on “Laughter,” “The Physiology of Smiling and Laughter,” “Psychology of Laughter,” and “Rituals of Laughter.”

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    • Chapman, Anthony J., and Hugh C. Foot. Eds. 1976. Humour and laughter: Theory, research and applications. London: John Wiley.

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      A must read for every student and scholar interested in humor and laughter. The third edition of the book was issued in 1996 by Transaction Publishers, New Brunswick, New Jersey.

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      • Darwin, Charles. 1872. The expression of the emotions in man and animals. London: John Murray.

        DOI: 10.1037/10001-000Save Citation »Export Citation »E-mail Citation »

        A must read for every student and scholar interested in emotions and their nonverbal expression. Contains many interesting descriptions of laughter (the “expression of mere joy”) and hypotheses on morphological features of laughter with changing laughter intensity.

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        • Devereux, Paul G., and Kathi L. Heffner. 2007. Psychophysiological approaches to the study of laughter. In Oxford handbook of methods in positive psychology. Edited by A. D. Ong and M. H. M. van Dulmen, 233–249. New York: Oxford Univ. Press.

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          Overview chapter on laughter research in relation to positive psychology. Targets the laughter morphology, measurement, and its possible links to health and well-being.

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          • Ekman, Paul, and Erika Rosenberg. 2005. What the face reveals: Basic and applied studies of spontaneous expression using the Facial Action Coding System (FACS). 2d ed. New York: Oxford Univ. Press.

            DOI: 10.1093/acprof:oso/9780195179644.001.0001Save Citation »Export Citation »E-mail Citation »

            Collection of basic and applied studies on nonverbal expressions assessed by the Facial Action Coding System. Suitable for students and advanced researchers. Entails findings on personality and laughter, laughter expression, laughter and its relation to grief reduction severity, agreeableness, and humor appreciation, laughter in psychotherapeutic interaction, and relation of smiling and laughter.

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            • Glenn, Philipp. 2003. Laughter in interaction. Cambridge, UK: Cambridge Univ. Press.

              DOI: 10.1017/CBO9780511519888Save Citation »Export Citation »E-mail Citation »

              Focus on conversation analysis. Suitable for students and advanced scholars interested in laughter functions.

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              • Gregory, Joshua C. 2013. The nature of laughter. London: Routledge.

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                Early account on laughter types, development, laughter in emotions (i.e., relief, pleasure) and tickling, and social functions. The original work was published in 1924 and republished in 2013.

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                • Martin, Rod A. 2001. Humor, laughter, and physical health: Methodological issues and research findings. Psychological Bulletin 127:504–519.

                  DOI: 10.1037/0033-2909.127.4.504Save Citation »Export Citation »E-mail Citation »

                  Review article on all research examining effects of humor and laughter up until 2000. Not specific to laughter but also covering studies on the topic.

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                  • Provine, Robert. 2001. Laughter: A scientific investigation. New York: Penguin.

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                    Often cited, easy to read, and gives an overview of ten years of research by the author. Needs to be followed up by a reading of the accompanying scientific articles.

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                    • Raulin, Jules Marie. 1900. Le rire et les exhilarants. Paris: Baillière.

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                      Early psychophysiological study of laughter and its elicitors. In French.

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                      • Wild, Barbara, Frank A. Rodden, Wolfgang Grodd, and Willibald Ruch. 2003. Neural correlates of laughter and humour: A review. Brain 126:2121–2138.

                        DOI: 10.1093/brain/awg226Save Citation »Export Citation »E-mail Citation »

                        Review article on investigations into the neurological correlates of humor and laughter. Collates and evaluates the studies published in the previous two decades.

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                        Journals

                        Empirical literature on laughter has steadily grown, mainly since the year 2000. The natural home of laughter studies is in journals concerned with behavior, emotion, and linguistics (pragmatics). Studies can be found in the Journal of Nonverbal Behavior, Evolution and Human Behavior, and the International Journal of Psychophysiology, the outlets for studies on the morphology of laughter and its occurrence (in humans and other primates). Also, with laughter being often linked to emotions or emotional encounters, articles can be found in Emotion, Motivation and Emotion, and Cognition and Emotion. Journal of Pragmatics entails works on the functions of laughter (i.e., in conversations). The journal Humor: International Journal of Humor Research is the official journal of the International Society for Humor Studies (ISHS). It is interdisciplinary and covers a wide range of scientific topics in humor and laughter research.

                        Phylogenetic Development

                        Human laughter has been estimated to be about five to seven million years old (depending on estimations of the occurrence of speech, as can be followed up, for example, in Davila-Ross, et al. 2009). It is safe to assume that laughter, like other utterances such as moans, sighs, cries, developed before speech evolved and served as an expressive-communicative signal. Van Hooff 1972 theorized that laughter and smiling could be viewed as displays with a different phylogenetic origin that have converged considerably in homo (see also Preuschoft 1995). In this view, laughter is supposed to have evolved from the silent bared-teeth display or play face, which is often accompanied by quick and shallow, rather staccato breathing (in some species the breathing may be vocalized). It occurs in mock-fighting/social play and tickling. Vettin and Todt 2005 compares macaques, chimpanzees, and human laughter in play and social situations. Their study provided further evidence that human laughter evolved from a play-signal of non-human primates. Interestingly, the authors of this paper also raised the question about the importance of the relationship of facial and vocal play signals in the evolution of human laughter. Another important finding of this study was the fact that the intra-individual intra-bout variability was high or higher than the interindividual variability in all three species. In similar vein, Davila-Ross, et al. 2009 compares the acoustics of play vocalizations (induced by tickling) in different primate species and consequently argued (based on van Hooff 1972 and later Vettin and Todt 2005) that human laughter evolved from an exhalation-based play signal in the common ancestor. Also, Meyer, et al. 2007 finds parallels in human and monkey laughter sounds for their occurrence in social/situational contexts and functional anatomy. Ruch and Ekman 2001 (cited under Morphology of Laughter) explains in detail the makeup of laughter sounds, hypothesizing that these sounds developed before speech (i.e., laughter being inarticulate sounds). Gervais and Wilson 2005 gives a theoretical account on the “ultimate evolutionary origins of laughter and humor” (p. 395). Panksepp 2005 gives a brief overview on how human laughter and joy link to related behaviors in other animals.

                        • Davila-Ross, Marina, Michael J. Owren, and Elke Zimmermann. 2009. Reconstructing the evolution of laughter in great apes and humans. Current Biology 19:1106–1111.

                          DOI: 10.1016/j.cub.2009.05.028Save Citation »Export Citation »E-mail Citation »

                          Empirical article investigating “play” vocalizations of juvenile orangutans (Pongo pygmaeus), gorillas (Gorilla gorilla), chimpanzees (Pan troglodytes), and bonobos (P. paniscus), as well as tickle-induced laughter of human infants.

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                          • Gervais, Matthew, and David S. Wilson. 2005. The evolution and functions of laughter and humor: A synthetic approach. Quarterly Review of Biology 80:395–430.

                            DOI: 10.1086/498281Save Citation »Export Citation »E-mail Citation »

                            Theoretical perspective on the development of laughter (and humor).

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                            • Meyer, Martin, Simon Baumann, Dirk Wildgruber, and Kai Alter. 2007. How the brain laughs. Behavioural Brain Research 182:245–260.

                              DOI: 10.1016/j.bbr.2007.04.023Save Citation »Export Citation »E-mail Citation »

                              Review article and important resource for both students and researchers.

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                              • Panksepp, Jaak. 2005. Beyond a joke: From animal laughter to human joy. Science 308:62–63.

                                DOI: 10.1126/science.1112066Save Citation »Export Citation »E-mail Citation »

                                Brief overview article on the links between laughterlike vocalizations in humans and other mammals.

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                                • Preuschoft, S. 1995. Laughter and ‘smiling’ in Macaques—an evolutionary perspective. Utrecht, the Netherlands: Univ. of Utrecht.

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                                  A must read for every student and advanced researcher interested in the phylogenetic development of laughter.

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                                  • Van Hooff, J. A. R. A. M. 1972. A comparative approach to the phylogeny of laughter and smiling. In Non–verbal communication. Edited by R. A. Hinde, 209–240. Cambridge, UK: Cambridge Univ. Press.

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                                    A must read for every student and advanced researcher interested in the phylogenetic development of laughter.

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                                    • Vettin, Julia, and Dietmar Todt. 2005. Human laughter, social play, and play vocalizations of non–human primates: An evolutionary approach. Behavior 142:217–240.

                                      DOI: 10.1163/1568539053627640Save Citation »Export Citation »E-mail Citation »

                                      Empirical article studying the play related vocalizations in Barbary macaques, chimpanzees, and humans.

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                                      Ontogenetic Development

                                      Laughter is an innate behavior—not a learned behavior. The facial laughter–related configurations are already occurring in prenatal infants: Reissland, et al. 2011 investigates the facial “laughter gestalt” in prenatal infants, investigating clusters of co–occurring facial features found in adult laughter, and found that the facial laughter gestalt emerges prebirth. Also, cases of gelastic epilepsy among neonates demonstrate that all laughter-related structures are functional at the date of birth (face and voice). Makagon, et al. 2008 presents further evidence for the innateness of laughter, basing on the fact that laughter is observable among deaf (and blind) children and adults, who could not learn the behaviors from observing others (visually or auditorily). Makagon, et al. 2008 shows that the laughter of normally hearing and deaf adults was highly similar in its acoustic characteristics. In line with this, findings on brain-damaged patients suggest that individuals with a bilateral damage in speech and motor areas (which hinders them vocalizing voluntarily) still display involuntarily produced emotion vocalizations, such as laughter, as Scheiner, et al. 2002 points out. This indicates a link of laughter to older vocal productions systems and unlearnt vocalizations. Sroufe and Waters 1976 discusses how laughter typically emerges around the fourth month of an infants’ life. In such young infants, laughter is mostly elicited by sensory stimulation (tactile, auditory stimulation, visual stimuli). Later, laughter elicitors are gaining complexity (i.e., play, amusement). Rothbart 1973 lays out a theoretical model, which conditions elicit laughter: laughter stems from tension-release in secure contexts. Nwokah, et al. 1993 was able to show that by the age of three, the duration and acoustic complexity of laughter starts to resemble adult laughter, whereas the fundamental frequency is still higher compared to adults. Furthermore, Nwokah, et al. 1994 shows the development of the social function of laughter in interaction within the first two years (i.e., the timing of coactive laughter becoming closer during the second year compared to the first year). Elicitors of laughter change during the course of development (in interaction with the environment), and also the ability to regulate laughter is linked to development. Ceschi and Scherer 2003 investigates the ability to regulate laughter in children of different age groups and found age-related differences in the ability to down-regulate/suppress amusement.

                                      • Ceschi, Grazia, and Klaus Scherer. 2003. Children’s ability to control the facial expression of laughter and smiling: Knowledge and behaviour. Cognition and Emotion 17:385–411.

                                        DOI: 10.1080/02699930143000725Save Citation »Export Citation »E-mail Citation »

                                        Empirical article investigating the ability to suppress laughter in children and mainly facial laughter suppression. Group under investigation: seven- and ten-year-old children. They found shorter laughter duration and more facial control markers but no differences in laughter frequency in suppressed laughter compared to unrestrained laughter.

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                                        • Makagon, Maja M., E. Sumie Funayama, and Michael J. Owren. 2008. An acoustic analysis of laughter produced by congenitally deaf and normally hearing college students. Journal of the Acoustical Society of America 124:472–483.

                                          DOI: 10.1121/1.2932088Save Citation »Export Citation »E-mail Citation »

                                          Empirical article investigating the acoustics of laughter in deaf and hearing college students. The produced laughs by hearing and deaf students were highly similar. The laughs of deaf students were of lower amplitude and longer duration, most likely due to a combination of physiological and social factors generally affecting deaf individuals.

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                                          • Nwokah, Evangeline E., Patricia Davies, Asad Islam, Hui-Chin Hsu, and Alan Fogel. 1993. Vocal affect in three-year-olds: A quantitative acoustic analysis of child laughter. Journal of the Acoustic Society of America 94:3076–3090.

                                            DOI: 10.1121/1.407242Save Citation »Export Citation »E-mail Citation »

                                            Empirical article investigating laughter acoustics in mother-child interactions. The average laughter duration was 200 milliseconds to 220 milliseconds, the fundamental frequency ranged from 270 Hz to 2900 Hz for different seven “laughter types.”

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                                            • Nwokah, Evangeline E., Hui-Chin Hsu, Olga Dobrowolska, and Alan Fogel. 1994. The development of laughter in mother–infant communication: Timing parameters and temporal sequences. Infant Behavior and Development 17:23–35.

                                              DOI: 10.1016/0163–6383(94)90019–1Save Citation »Export Citation »E-mail Citation »

                                              Empirical article investigating laughter in mother-child interactions, showing the changes in the occurrence of laughter within interaction over the first two years (e.g., the timing of coactive laughter, the quantity of self-repetitive and reciprocal laughter).

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                                              • Reissland, Nadja, Brian Francis, James Mason, and Karen Lincoln. 2011. Do facial expressions develop before birth? PLoS One 6:e24081.

                                                DOI: 10.1371/journal.pone.0024081Save Citation »Export Citation »E-mail Citation »

                                                Empirical article investigating facial displays over the course of development (pre-birth). Group under investigation: Babies in uterus.

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                                                • Rothbart, Mary. 1973. Laughter in young children. Psychological Bulletin 80:247–256.

                                                  DOI: 10.1037/h0034846Save Citation »Export Citation »E-mail Citation »

                                                  Theoretical article describing the conditions under which laughter may be elicited in young children (i.e., the perception of a safe situation, alongside arousal).

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                                                  • Scheiner, Elisabeth, Kurt Hammerschmidt, Uwe Jürgens, and Petra Zwirner. 2002. Acoustic analyses of developmental changes and emotional expression in the preverbal vocalizations of infants. Journal of Voice 16:509–529.

                                                    DOI: 10.1016/S0892–1997(02)00127–3Save Citation »Export Citation »E-mail Citation »

                                                    Empirical article investigating developmental changes in uttered vocalizations (laughter being one of them). Group under investigation: Neonates (seven to ten weeks old), until the age of fifty-three to fifty-eight weeks.

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                                                    • Sroufe, L. Alan, and Everett Waters. 1976. The ontogenesis of smiling and laughter: A perspective on the organization of development in infancy. Psychological Review 83:173–189.

                                                      DOI: 10.1037/0033–295X.83.3.173Save Citation »Export Citation »E-mail Citation »

                                                      Widely cited article, a classic work on developmental aspects of smiling and laughter. Group under investigation: children of different age groups.

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                                                      Laughter in Nonhuman Animals

                                                      Man is not the only animal that laughs. Many writers have described the similarities between ape and human laughter (see also Phylogenetic Development). Especially among juvenile chimpanzees a “play face” with associated vocalizations was noted to accompany actions such as play, tickling, or play biting/rough–and–tumble play (see also Phylogenetic Development). Berntson, et al. 1989 provides recordings from a juvenile male chimpanzee during active play, which showed a typical temporal structure, with periodic louder voiced and voiceless components. Cordoni and Palagi 2011, based on the findings of van Hooff 1972 (cited under Phylogenetic Development), finds that “laughter” aims at prolonging play sessions among chimpanzees and is more frequent in social compared to nonsocial play in young humans and chimpanzees. Davila-Ross, et al. 2009 suggests great ape laughter can be found in at least three laughter types that differ in their acoustic structure: spontaneous laughter, laughter replies, and delayed laughter. Furthermore, Burgdorf, et al. 2008; Burgdorf, et al. 2011; and Panksepp and Burgdorf 2003 suggest that rats emit “laughter-like” vocalizations: the researchers repeatedly found 50 Hz ultrasonic vocalizations in rats, which were typically elevated by hedonic stimuli, elicited by tickling and suppressed by aversive stimuli. Rates of these stimuli were positively correlated with the rewarding value of the eliciting stimulus, and playbacks were rewarding, too. Also, the pharmacological neural substrates of the 50 Hz ultrasonic vocalizations were found to converge with those of humans’ positive affect. Beyond the experience of positive affect, Rygula, et al. 2012 further suggests that “laughing” rats become “more optimistic”: The authors of this paper found that “tickled” rats (which exhibited 50 Hz ultrasonic sounds in response to the tickling) were acting in a way that could be interpreted as more optimistic in a decision making task under ambiguity than rats that were just handled. Nevertheless, similarly to human laughter utterances and individual differences in call emission and occurrence have been found, suggesting that those 50 Hz calls do not only serve emotional expressive functions but also social-communicative functions, as Schwarting, et al. 2007 and Wöhr, et al. 2008 show. Furthermore, it was also documented that laughterlike vocalizations were acquired by domesticated species: Gogoleva, et al. 2011 finds a similarity between human laughter and the structure of tame silver fox cackles and pants (calls produced exclusively by tame foxes toward humans).

                                                      • Berntson, Gary, Sarah T. Boysen, Harold R. Bauer, and Michael S. Torello. 1989. Conspecific screams and laughter: Cardiac and behavioral reactions of infant chimpanzees. Developmental Psychobiology 22:771–787.

                                                        DOI: 10.1002/dev.420220803Save Citation »Export Citation »E-mail Citation »

                                                        Empirical article investigating cardiac and behavioral responses of young chimpanzees to hearing “laughter”, screams, and white noise. Results show that “laughter” evoked vocalizations and cardiac acceleration.

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                                                        • Burgdorf, Jeffrey, Roger A. Kroes, Joseph R. Moskal, James G. Pfaus, Stefan M. Brudzynski, and Jaak Panksepp. 2008. Ultrasonic vocalizations of rats (Rattus norvegicus) during mating, play, and aggression: Behavioral concomitants, relationship to reward, and self–administration of playback. Journal of Comparative Psychology 122:357–367.

                                                          DOI: 10.1037/a0012889Save Citation »Export Citation »E-mail Citation »

                                                          A must read for students and researchers who are interested in “laughter” vocalizations in mammals.

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                                                          • Burgdorf, Jeffrey, Jaak Panksepp, and Joseph R. Moskal. 2011. Frequency–modulated 50kHz ultrasonic vocalizations: A tool for uncovering the molecular substrates of positive affect. Neuroscience & Biobehavioral Reviews 35:1831–1836.

                                                            DOI: 10.1016/j.neubiorev.2010.11.011Save Citation »Export Citation »E-mail Citation »

                                                            Empirical article that investigates the relationship between “laughter-like” vocalizations in rats and positive affect. Entails interesting ideas of potential advances in the treatment of depression.

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                                                            • Cordoni, Giada, and Elisabetta Palagi. 2011. Ontogenetic trajectories of chimpanzee social play: Similarities with humans. PLoS One 6:e27344.

                                                              DOI: 10.1371/journal.pone.0027344Save Citation »Export Citation »E-mail Citation »

                                                              Empirical article comparing the phenomenon of social play in chimpanzees and humans: frequency of play, playmate choice, play modality, play asymmetry, complexity, signal frequency, signal timing, preferential use of different play signals, and play signal and play asymmetry.

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                                                              • Davila-Ross, Marina, Michael J. Owren, and Elke Zimmermann. 2009. Reconstructing the evolution of laughter in great apes and humans. Current Biology 19:1106–1111.

                                                                DOI: 10.1016/j.cub.2009.05.028Save Citation »Export Citation »E-mail Citation »

                                                                Empirical article investigating the hypothesis that human emotional expressions, such as laughter, have their origins in ancestral nonhuman primate displays.

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                                                                • Gogoleva, Svetlana S., Ilya A. Volodin, Elena V. Volodina, Anastasia V. Kharlamova, and Luydmila N. Trut. 2011. Explosive vocal activity for attracting human attention is related to domestication in silver fox. Behavioural Processes 86:216–221.

                                                                  DOI: 10.1016/j.beproc.2010.12.001Save Citation »Export Citation »E-mail Citation »

                                                                  Empirical article investigating the structural similarity between human laughter and vocalizations of domesticated foxes (in response to humans only).

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                                                                  • Panksepp, Jaak, and Jeffrey Burgdorf. 2003. ‘Laughing’ rats and the evolutionary antecedents of human joy? Physiology and Behavior 79:533–547.

                                                                    DOI: 10.1016/S0031–9384(03)00159–8Save Citation »Export Citation »E-mail Citation »

                                                                    Review and theory article putting forward the hypothesis that 50 Hz ultrasonic rat vocalizations may resemble the childhood laughter in social play and reflect positive affect.

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                                                                    • Rygula, Rafal, Helena Pluta, and Piotr Popik. 2012. Laughing rats are optimistic. PLoS One 7:e51959.

                                                                      DOI: 10.1371/journal.pone.0051959Save Citation »Export Citation »E-mail Citation »

                                                                      Empirical article investigating the link between the directly measured positive affective state and decision making under uncertainty in animals.

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                                                                      • Schwarting, Rainer K. W., Nikita Jegan, and Markus Wöhr. 2007. Situational factors, conditions and individual variables which can determine ultrasonic vocalizations in male adult Wistar rats. Behavioral Brain Research 182:208–222.

                                                                        DOI: 10.1016/j.bbr.2007.01.029Save Citation »Export Citation »E-mail Citation »

                                                                        Empirical article providing evidence that the 50 Hz (and also 22 Hz) ultrasonic vocalizations in rats serve social/communicatory and motivational/emotional functions, and are not solely expressing a positive affective state.

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                                                                        • Wöhr, Markus, Bart Houx, Rainer K. W. Schwarting, and Berry Spruijt. 2008. Effects of experience and context on 50-kHz vocalizations in rats. Physiology & Behavior 93:766–776.

                                                                          DOI: 10.1016/j.physbeh.2007.11.031Save Citation »Export Citation »E-mail Citation »

                                                                          Empirical article showing in two experiments that rats emit 50 Hz ultrasonic vocalizations that may not reflect a positive emotional state but may have social functions (i.e., being omitted after the separation from cage mates) and being influenced by the experience of the animal and individual differences.

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                                                                          The Morphology of Laughter

                                                                          Laughter is a more complex behavior than smiling and/or facial configurations. But also lacrimation, respiration, body movements, body posture, physiological changes, and vocalization (phonation, resonance) need to be considered for a comprehensive description of laughter morphology. For a general introduction, Ruch and Ekman 2001 provides a good overview on laughter segmentation and morphology. To describe a laughter event, the term “laughter bout” was coined to refer to a whole behavioral-acoustic laughter event. A laughter bout is split into three parts: an onset (i.e., facial actions already occur but no vocalization yet, this part may be brief in the case of explosive laughter), an apex (i.e., this part, the vocalization or forced exhalation occurs), and an offset (i.e., after the vocalization; often a long-lasting smile fading out smoothly). The laughter vocalization part is composed of laugh cycles (i.e., repetitive laugh–pulses interspersed with pauses). There is laughter with only one or two pulses (as in an “ha”-type “exclamation laughs”), but studies typically reported four pulses to be most frequent. The upper number of pulses in a laugh cycle was shown to be limited by the lung volume. In the sections Face, Respiration, Laughter Acoustics, Body, Physiological Changes the morphology of laughter is discussed in more detail.

                                                                          Face

                                                                          Typically, studies on laughter facial features utilized facial EMG or the Facial Action Coding System (FACS) by Paul Ekman and Wallace Friesen to measure the facial actions occurring during a laughter bout. As laughter is often associated with the emotion of joy, the facial configuration named the “Duchenne Display” (the simultaneous and symmetric contraction of the orbicularis oculi pars orbitalis muscle and the zygomatic major muscle) served as a first starting point for looking at laughter facial features. And still, the “Duchenne laughter” is the most commonly investigated laughter facial feature configuration in psychological research. For example, Keltner and Bonanno 1997 studies facial responses of grieving spouses. Campos, et al. 2013 looks at facial expressions of eight positive emotions. Juckel, et al. 2011 shows facial responses in response to humor and neural correlates. Hofmann 2014 shows the facial features of laughter at different stages of intensity. Duchenne laughter includes the Duchenne markers, typically accompanied by an opened mouth (and maybe a lowered jaw), as well as forced exhalation/vocalization. Thus, laughter also includes the relaxation of some muscles (masseter, pterygoids) that are responsible for the lowering of the jaw and the expulsion of air through the mouth. Still, studies on natural and posed amusement/joyful laughter have reported the occurrence of other facial markers, too. This may be due to several reasons: firstly, additional muscles might be involved due to auxiliary movements (i.e., muscles around the mouth). Secondly, the intensity of the laughter and conscious attempts to up- or down-regulate laughter may cause different muscular involvement. Third, it is not known whether qualitatively different laughter types would entail specific facial features. Fourth, not all facial actions may be active at all times during laughter (i.e., in in- or decreasing laughter intensity). Therefore, the time course of facial feature appearance might be indicative of which further facial actions appear/vanish from the face. At the apexes of amusement/joyful laughter, following facial actions beyond the Duchenne markers were reported to occur in the upper and lower face: In the upper face, the inner and outer brow raise (i.e., reported in Krumhuber and Scherer 2011, as well as in Scherer and Ellgring 2007), eyebrow-lowering frowning, nose wrinkling (reported by Reissland, et al. 2011 [cited under Ontogenetic Development] and Ruch, et al. 2013), head back and eyes up, mostly basing on data from posed expressions. In the lower face, the deepening of the nasolabial furrow, lip stretching, and cheek dimpling were reported. Future studies need to clarify what the role of these facial features is (i.e., being markers of intensity or laughter regulation, markers of specific laughter types, markers of auxiliary actions).

                                                                          • Campos, Belinda, Michelle N. Shiota, Dacher Keltner, Gian C. Gonzaga, and Jennifer L. Goetz. 2013. What is shared, what is different? Core relational themes and expressive displays of eight positive emotions. Cognition and Emotion 27:37–52.

                                                                            DOI: 10.1080/02699931.2012.683852Save Citation »Export Citation »E-mail Citation »

                                                                            Empirical article investigating the expressive patterns of eight positive emotions in posed expressions.

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                                                                            • Hofmann, Jennifer. 2014. Intense or malicious? The decoding of eyebrow-lowering frowning in laughter animations depends on the presentation mode. Frontiers in Psychology 5:1306.

                                                                              DOI: 10.3389/fpsyg.2014.01306Save Citation »Export Citation »E-mail Citation »

                                                                              Empirical article investigating the decoding of laughter animations with experimentally varied facial features.

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                                                                              • Juckel, Georg, Roland Mergl, and Martin Brüne, et al. 2011. Is evaluation of humorous stimuli associated with frontal cortex morphology? A pilot study using facial micro–movement analysis and MRI. Cortex 47:569–574.

                                                                                DOI: 10.1016/j.cortex.2010.04.004Save Citation »Export Citation »E-mail Citation »

                                                                                Empirical article investigating cortical and facial responses to humorous stimuli.

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                                                                                • Keltner, Dacher, and George A. Bonanno. 1997. A study of laughter and dissociations: Distinct correlates of laughter and smiling during bereavement. Journal of Personality and Social Psychology 73:687–702.

                                                                                  DOI: 10.1037/0022–3514.73.4.687Save Citation »Export Citation »E-mail Citation »

                                                                                  Empirical article investigating the occurrence of laughter and smiling in times of grief over the loss of a spouse.

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                                                                                  • Krumhuber, Eva G., and Klaus Scherer. 2011. Affect bursts: Dynamic patterns of facial expression. Emotion 4:825–841.

                                                                                    DOI: 10.1037/a0023856Save Citation »Export Citation »E-mail Citation »

                                                                                    Empirical article investigating acted expressions of emotions, amongst them joy/elation (including laughter).

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                                                                                    • Ruch, Willibald, Jennifer Hofmann, and Tracey Platt. 2013. Investigating facial features of four types of laughter in historic illustrations. European Journal of Humor Research 1:98–118.

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                                                                                      Two studies investigating the facial features of four different laughter types (joyful, intense, schadenfreude laughter, and grinning) in a combined en- and decoding approach.

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                                                                                      • Scherer, Klaus, and Heiner Ellgring. 2007. Are facial expressions of emotion produced by categorical affect programs or dynamically driven by appraisal? Emotion 7:113–130.

                                                                                        DOI: 10.1037/1528–3542.7.1.113Save Citation »Export Citation »E-mail Citation »

                                                                                        Empirical article investigating acted expressions of emotions (fourteen different emotions) and analyzing the facial action units going along with the acted expressions.

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                                                                                        Respiration

                                                                                        Laughter typically consists of an initial forced exhalation, followed by a more or less sustained sequence of repeated expirations of high frequency and low amplitude, which may or may not be phonated (also Voice). Laughter is produced at low lung volume and no inspiration is necessary before as Bright, et al. 1986 shows. The laugh cycles are normally initiated around the functional residual capacity, meaning at the level that the lung volume usually has after a normal expiration. The laugh cycles usually terminate around the residual volume (i.e., the volume remaining in the lung after maximal expiration) or sometimes even exceed the level of maximal voluntary exhalation, as reported in Filippelli, et al. 2001. Thus, the initial forced exhalation in laughter is expelling the “tidal volume,” and the following sequence of laugh-pulses is based on the expiratory reserve volume in the lung. The depth of respiration increases in laughter to up to 2.5 times the amplitude compared to resting respiration. This increase is mainly due to a stronger expiration. In some laughter episodes, inspiration may add to the amplitude, if single deep inhalations intersperse the expiratory sequences. The rhythmic laughter respiration pattern is produced by saccadic contractions of auxiliary expiration muscles (i.e., muscles that are typically passive during normal expiration [diaphragm, abdominal, and rib cage muscles). The respiratory muscles function in interplay with the larynx. Without any closing of the glottis there may be only a few forced exhalations, but the adduction (closing) of the glottis prevents the air from being exhaled too quickly and thus allows the building up and maintaining of subglottal air pressure (see also Ruch and Ekman 2001, cited under Morphology of Laughter). Luschei, et al. 2006 reports brief amplitude bursts of activity in the thyroarytenoid and lateral cricoarytenoid laryngeal adductors in spontaneous laughter, as well as out-of-phase activity by the posterior cricoarytenoid laryngeal adductor. The cricothyroid muscle is unmodulated during laughter. The pressure modulations are indicative of when (and if) phonation occurs in the laughter, as shown in Filippelli, et al. 2001 and Luschei, et al. 2006. The heightened pressure takes the air stream up the airways through the larynx where the rhythmic closing and opening of the glottis interrupts the air stream. These vibrations are carried through the vocal tract. The shape of the vocal tract amplifies or dampens certain frequency spectra, and finally the air escapes through the mouth or the nose.

                                                                                        • Bright, K. E., T. J. Hixon, and J. D. Hoit. 1986. Respiration as a laughing matter. In WHIMSY IV. Edited by D. L. F. Nilsen and A. P. Nilsen, 147–148. Tempe: Arizona State Univ.

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                                                                                          Empirical article investigating respiration in laughter.

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                                                                                          • Filippelli, Mario, Riccardo Pellegrino, and Iacoppo Iandelli, et al. 2001. Respiratory dynamics during laughter. Journal of Applied Physiology 90:1441–1446.

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                                                                                            Empirical article investigating a variety of respiratory components during laughter: lung and chest mechanics, chest wall volume, and esophageal and gastric pressures (adults participants).

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                                                                                            • Luschei, Erich S., Lorraine O. Ramig, Eileen M. Finnegan, Kristen K. Baker, and Marshall E. Smith. 2006. Patterns of laryngeal electromyography and the activity of the respiratory system during spontaneous laughter. Journal of Neurophysiology 96:442–450.

                                                                                              DOI: 10.1152/jn.00102.2006Save Citation »Export Citation »E-mail Citation »

                                                                                              Empirical article investigating the measures of the behavior of the respiratory system with laryngeal muscle electromyography (EMG) during spontaneous laughter (adult participants, healthy or with Parkinson’s).

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                                                                                              Laughter Acoustics

                                                                                              The laughter sounds are produced by a series of rapid, continuous, stereotypic laryngeal adjustments. They are split in four stages: interpulse pause (an instant of quiet between the audible moments of laughter), adduction (closing) of the arytenoid cartilages, vibration of vocal cords, and abduction (opening) of the arytenoid cartilages. The thyroarytenoid and (to a lesser extent) the cricothyroid muscles are involved in the closing of the glottis, and the opening is achieved by the posterior cricoarytenoid muscle (see Respiration). During the interpulse pause the arytenoid cartilages rest open. This allows the breath stream to flow unhindered through the larynx. The “h” sound is an eddy-current phenomenon created during the closing stage of the valvelike movements of the vocal folds. During the adduction stage, the arytenoid cartilages carry the cords toward each other, and when the glottal space has been narrowed to a small slit, the cords begin to vibrate. Moore and von Leden 1958 reports that it takes about 10 milliseconds to accomplish the transition from quiescence to full vibration and that changes in vibratory curve contours and in the length of cycles occur with the progression of the laugh-pulse. There is a progressive diminution of the mesial excursion of the cords and the slowing of the cord movement as the interarytenoid space enlarges. In the sample laugh-pulse provided in Moore and von Leden 1958, there is a progressive drop of about thirty cycles per second. Like in speech also in laughter females have a higher fundamental frequency than men. There is no cortically controlled articulation in laughter and the sound uttered in phonated laughter often resembles the central vowel schwa, or /e/. For the production of this “neutral vowel” the mouth is opened and the jaw lowered, with other articulators passive. The sound is also influenced by facial actions (i.e., degree of jaw lowering). Vettin and Todt 2004 is a report on the findings on the frequency of laughter occurrence in different conditions, the duration of laughter bouts and intervals, fundamental frequency ranges for males and females and results on intra- and inter-individual variability in laughter acoustics. Furthermore, variations were related to the degree of arousal/exhilaration, or the laughter type, see for example Bryant and Aktipis 2014.

                                                                                              • Bryant, Gregory A., and C. Athena Aktipis. 2014. The animal nature of spontaneous human laughter. Evolution and Human Behavior.

                                                                                                DOI: 10.1016/j.evolhumbehav.2014.03.003Save Citation »Export Citation »E-mail Citation »

                                                                                                Empirical article investigating the acoustic features of two laughter types: spontaneous and posed laughter.

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                                                                                                • Moore, Paul, and Hans Von Leden. 1958. Dynamic variations of the vibratory pattern in the normal larynx. Folia Phoniatrica et Logopaedica 4:205–238.

                                                                                                  DOI: 10.1159/000262819Save Citation »Export Citation »E-mail Citation »

                                                                                                  Investigates what happens in the larynx, in different sounds, produced voluntarily and involuntarily.

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                                                                                                  • Vettin, Julia, and Dietmar Todt. 2004. Laughter in conversation; features of occurrence and acoustic structure. Journal of Nonverbal Behavior 28:93–115.

                                                                                                    DOI: 10.1023/B:JONB.0000023654.73558.72Save Citation »Export Citation »E-mail Citation »

                                                                                                    Empirical article investigating differences in laughter in different conversational contexts. Results show large within and between differences in participants in laughter occurrence across contexts, no gender differences in laughter bout frequency, a mean F0 for men of 171 Hz and 315 Hz in women.

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                                                                                                    Body, Physiological Changes

                                                                                                    Body movements have received the least attention in the study of laughter. While some laughter body movements are associated with the respiratory movements (i.e., the backward tilt of the head facilitates the forced exhalations, and the forced inhalation interrupting two laughter cycles raises and straightens the trunk), others may be due to laughter intensity, regulation, laughter types, or personal laughter styles. There are also body movements not coupled with respiration actions, but their exact list and the conditions under which they emerge are not known. Thus far, violent laughter was rarely induced in laboratory studies, and therefore one has to rely on observations and self-reports such as Hall and Allin 1897. These authors issued an eleven-item questionnaire on tickling, fun, wit, humor, and laughing as a supplement to American Journal of Psychology. A further body movement that was observed in laughter is the abrupt bending of the knees, due to a relaxation of the muscles: Overeem, et al. 2004 investigates periods of amusement laughter and found that these laughs evoked an H-reflex depression (i.e., a depressing effect on spinal motor neuron excitability and a consequently relaxed muscle tone). This phenomenon widely occurs in spontaneous laughter. Beyond visible laughter body movements and respiration, other physiological changes go along with laughter. For example, amusement laughter goes along with increased electrodermal and cardiovascular arousal as Sugawara, et al. 2010 shows, and increased energy expenditure, as reported by Buchowski, et al. 2007.

                                                                                                    • Buchowski, Maciej S., Karen M. Majchrzak, Kerstin Blomquist, Kong Y. Chen, Daniel W. Byrne, and Jo-Anne Bachorowski. 2007. Energy expenditure of genuine laughter. International Journal of Obesity 31:131–137.

                                                                                                      DOI: 10.1038/sj.ijo.0803353Save Citation »Export Citation »E-mail Citation »

                                                                                                      Empirical article investigating the level of the energy expenditure and heart rate during genuine laughter (adult participants). Laughter leads to a 10–20 percent increase in energy expenditure and heart rate above resting values.

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                                                                                                      • Hall, G. S., and A. Allin. 1897. The psychology of tickling, laughing, and the comic. American Journal of Psychology 9:1–41.

                                                                                                        DOI: 10.2307/1411471Save Citation »Export Citation »E-mail Citation »

                                                                                                        Classic article on the self-reported body movements and behaviors occurring during laughter. A must read to anybody interested in laughter.

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                                                                                                        • Overeem, Sebastiaan, Walter Taal, E. Öcal Gezici, Gert J. Lammers, and J. Gert van Dijk. 2004. Is motor inhibition during laughter due to emotional or respiratory influences? Psychophysiology 41:254–258.

                                                                                                          DOI: 10.1111/j.1469–8986.2003.00145.xSave Citation »Export Citation »E-mail Citation »

                                                                                                          Empirical article comparing the effects of laughter and several respiratory movements (such as coughing) on spinal motor excitability to show their respective influences (healthy adult volunteers).

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                                                                                                          • Sugawara, Jun, Takashi Tarumi, and Hirofumi Tanaka. 2010. Effect of mirthful laughter on vascular function. American Journal of Cardiology 106:856–859.

                                                                                                            DOI: 10.1016/j.amjcard.2010.05.011Save Citation »Export Citation »E-mail Citation »

                                                                                                            Empirical article investigating the relationship of positive emotional states and cardiovascular health (healthy adult participants).

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                                                                                                            Laughter and the Brain

                                                                                                            In the sections Production and Perception, findings on neural correlates of laughter production and laughter perception are presented separately. To give a brief overview, for laughter production and related brain areas most studies have focused on the most widely known laughter elicitor: amusement induced by humorous stimuli (neuro-pathological forms of laughter are not covered here). This is most likely due to the ease with which amusement can be elicited in a laboratory setting where participants may be tied to recording devices and even restricted in their movements (i.e., in fMRI, head movements can lead to signal artifacts). Importantly for the case of amusement, distinctions between humor perception/processing, and the motor response (smiling and laughter) were reported, separating the understanding of content from the emotional and the motor response to it. Goel and Dolan 2001; Samson, et al. 2009; Vrticka, et al. 2013; and Wild, et al. 2006 all provide good reviews of these aspects. A few studies have included tickling as an eliciting condition, as well as posed (acted) laughter. Also, the regulation of laughter was studied (i.e., attempts to suppress laughter under tickling, as described in Wattendorf, et al. 2013, cited under Laughter and the Brain: Production). A few studies have also investigated the expression of laughter when electrically stimulating brain areas in patients (see also Pathological Laughter). With respect to the perception of laughter, the brain responses to passive listening of different types of laughter were investigated. Meyer, et al. 2007 focuses not only on human laughter but also on laughterlike vocalizations in monkeys and great apes, showing similarities and differences of the cerebral organization of this affective vocalization that occurs in several mammalian species.

                                                                                                            • Goel, Vinod, and Raymond D. Dolan. 2001. The functional anatomy of humor: Segregating cognitive and affective components. Nature Neuroscience 4:237–238.

                                                                                                              DOI: 10.1038/85076Save Citation »Export Citation »E-mail Citation »

                                                                                                              Empirical article investigating the processing of auditorily presented semantic and phonological jokes (puns). Participants further indicated the felt amusement toward the stimuli, responses toward understanding and feeling amused were separated. Method: fMRI.

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                                                                                                              • Meyer, Martin, Simon Baumann, Dirk Wildgruber, and Kai Alter. 2007. How the brain laughs. Comparative evidence from behavioral, electrophysiological and neuroimaging studies in human and monkey. Behavioral Brain Research 182:245–260.

                                                                                                                DOI: 10.1016/j.bbr.2007.04.023Save Citation »Export Citation »E-mail Citation »

                                                                                                                Review article describing the knowledge on behavioral and brain mechanisms of “laughter-like” vocalizations and the cerebral organization of laughter. Laughterlike vocalizations seem to recruit similar cortical and subcortical areas as those found in humans under laughter.

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                                                                                                                • Samson, Andrea C., Christian Hempelmann, Oswald Huber, and Stefan Zysset. 2009. Neural substrates of incongruity–resolution and nonsense humor. Neuropsychologia 47:1023–1033.

                                                                                                                  DOI: 10.1016/j.neuropsychologia.2008.10.028Save Citation »Export Citation »E-mail Citation »

                                                                                                                  Empirical article investigating the processing of incongruity-resolution and nonsense humor stimuli (cartoons). Method: fMRI.

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                                                                                                                  • Vrticka, Pascal, Jessica M. Black, and Allan L. Reiss. 2013. The neural processing of humour. Nature Reviews Neuroscience 14:860–868.

                                                                                                                    DOI: 10.1038/nrn3566Save Citation »Export Citation »E-mail Citation »

                                                                                                                    A must-read review article on the processing of different types of humorous stimuli and responses. Also targets laughter.

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                                                                                                                    • Wild, Barbara, Frank A. Rodden, Alexander Rapp, Michael Erb, Wolfgang Grodd, and Willibald Ruch. 2006. Humor and smiling: Cortical regions selective for cognitive, affective, and volitional components. Neurology 66:887–893.

                                                                                                                      DOI: 10.1212/01.wnl.0000203123.68747.02Save Citation »Export Citation »E-mail Citation »

                                                                                                                      Empirical article investigating the processing of funny and non-funny equivalents of cartoons in thirteen adult subjects. Method: fMRI. Results show differential activation for voluntary grinning versus spontaneous smiling under humor.

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                                                                                                                      Production

                                                                                                                      Amusement laughter is the most thoroughly studied laughter type. When seeing a humorous stimulus, a “motor planning of laughter” starts, as shown in Mobbs, et al. 2003. Then, the punchline occurs. This leads to a processing of the stimulus in terms of “understanding” of the humor and brain activation due to the “expression” of amusement (smiling and laughter). For the “understanding” increases in blood oxygenation level dependent (BOLD) activity in the left temporo–occipitoparietal junction and left prefrontal cortex, as well as a decrease of BOLD activity in the basal temporal lobes have been reported to correlate with the correct processing of the humorous stimulus, as Wild, et al. 2006 shows. Both Wattendorf, et al. 2013 and Wild, et al. 2006 show that the medial thalamus, the amygdala, and the hypothalamus were linked to the emotion felt—in this case, amusement. Amoss 2013 reports that laughter–specific activations occur in the orbitofrontal sites beginning with 200 milliseconds after the stimulus. Additionally, Amir, et al. 2013 describes that the (spontaneous) laughter production is linked to the SMA, with the coordination of the respiratory and laryngeal components in the midbrain and brainstem. Further evidence from patient studies suggested that the electrical stimulation of the left presupplementary motor area (SMA) or nucleus accumbens led to series of graduating smiles to laughs, with accompanying feelings of mirth/positive affect, for example reported in Okun, et al. 2004. When producing posed laughter (compared to spontaneous amusement laughter), the face area of the bilateral motor area (Brodmann Area [BA] 4), bilateral SMA, the right preuncus (BA7), and the bilateral–parietal cortices (BA7, BA40), as well as the bilateral insular cortices were found to be activated, as reported by Iwase, et al. 2002. Notably, Iwase, et al. 2002 further shows that the SMA was activated to a greater extent in posed laughter compared to laughing spontaneously. Furthermore, the involvement of the motor areas confirmed the volitional component of posed laughter. Juckel, et al. 2011 reports that the gray matter volume in the prefrontal cortex was associated with longer emotional reaction times in response to humorous stimuli, even when controlling for the age and alcohol intake of the participants. The authors of this paper also found that superior cognitive evaluations of humorous stimuli were mediated by larger prefrontal grey and white matter volumes, leading to a measurable reduction of speed in emotional expressivity (i.e., laughter).

                                                                                                                      • Amir, Ori, Irving Biederman, Zhuangjun Wang, and Xiaokun Xu. 2013. Ha ha! Versus Aha! A direct comparison of humor to non–humorous insight for determining the neural correlates of mirth. Cerebral Cortex. 25:1405–1413.

                                                                                                                        DOI: 10.1093/cercor/bht343Save Citation »Export Citation »E-mail Citation »

                                                                                                                        Empirical article investigating the processing of funny and non-funny equivalents of drawings. Method: fMRI.

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                                                                                                                        • Amoss, Richard. 2013. The good, the bad, and the funny: A neurocognitive study of laughter as a meaningful socio-emotional cue. Retrieved from Psychology Dissertations. Paper 123.

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                                                                                                                          Investigates responses to visually presented words, which were preceded by either laughs or environmental sounds (500 milliseconds versions of the International Affective Digitized Sounds). Method: ERP.

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                                                                                                                          • Iwase, Masao, Yasuomi Ouchi, and Hiroyuki Okada, et al. 2002. Neural substrates of human facial expression of pleasant emotion induced by comic films: A PET study. Neuroimage 17:758–768.

                                                                                                                            DOI: 10.1006/nimg.2002.1225Save Citation »Export Citation »E-mail Citation »

                                                                                                                            Empirical article investigating the processing of funny films, comparing spontaneous laughter and smiles and voluntary facial expressions of smiling/laughter. Method: PET, EMG.

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                                                                                                                            • Juckel, Georg, Roland Mergl, and Martin Brüne, et al. 2011. Is evaluation of humorous stimuli associated with frontal cortex morphology? A pilot study using facial micro–movement analysis and MRI. Cortex 47:569–574.

                                                                                                                              DOI: 10.1016/j.cortex.2010.04.004Save Citation »Export Citation »E-mail Citation »

                                                                                                                              Empirical article investigating the processing of and responses to a Mr. Bean movie.

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                                                                                                                              • Mobbs, Dean, Micheal D. Greicius, Eiman Abdel-Azim, Vinod Menon, Allan L. Reiss. 2003. Humor modulates the mesolimbic reward centers. Neuron 40:1041–1048.

                                                                                                                                DOI: 10.1016/s0896–6273(03)00751–7Save Citation »Export Citation »E-mail Citation »

                                                                                                                                Empirical article investigating the processing of funny and non-funny equivalents of cartoons, arguing that humor also triggers the reward associated regions in the brain. Method: fMRI.

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                                                                                                                                • Okun, Michael S., Dawn Bowers, and Utaka Springer, et al. 2004. What’s in a “smile”? Intra–operative observations of contralateral smiles induced by deep brain stimulation. Neurocase 10:271–279.

                                                                                                                                  DOI: 10.1080/13554790490507632Save Citation »Export Citation »E-mail Citation »

                                                                                                                                  Clinical case study. The stimulation of the nucleus accumbens leads to smiling and self-reported feelings of euphoria.

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                                                                                                                                  • Wattendorf, Elise, Birgit Westermann, Klaus Fiedler, Evangelia Kaza, Martin Lotze, and Marco R. Celio. 2013. Exploration of the neural correlates of ticklish laughter by functional magnetic resonance imaging. Cerebral Cortex 23:1280–1289.

                                                                                                                                    DOI: 10.1093/cercor/bhs094Save Citation »Export Citation »E-mail Citation »

                                                                                                                                    Empirical article investigating neural correlates toward tickling laughter and suppressed laughter under tickling. Method: fMRI.

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                                                                                                                                    • Wild, Barbara, Frank A. Rodden, Alexander Rapp, Michael Erb, Wolfgang Grodd, and Willibald Ruch. 2006. Humor and smiling: Cortical regions selective for cognitive, affective, and volitional components. Neurology 66:887–893.

                                                                                                                                      DOI: 10.1212/01.wnl.0000203123.68747.02Save Citation »Export Citation »E-mail Citation »

                                                                                                                                      Empirical article investigating the processing of funny and non-funny equivalents of cartoons. Method: fMRI.

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                                                                                                                                      Perception

                                                                                                                                      Meyer, et al. 2005 finds activations in the auditory and somatosensory fields primarily in the right hemisphere as well as the activation of brain regions that control motor functions (i.e., larynx) when listening to acted laughter (compared to speech and non-vocal sounds). Sander and Scheich 2001 and Sander and Scheich 2005 investigate brain region activations when passively listening to posed laughter encoded by professional actors. These researchers found activations in the amygdala (right–hemisphere advantage) which Meyer, et al. 2005 did not observe, as well as activations of the insula, and the auditory cortex. Sander and Scheich 2001 and Sander and Scheich 2005 consequently argue that the amygdala is primarily concerned with the recognition and expression of emotion and thus involved in the laughter processing. Still, as Meyer, et al. 2005 notes, the involvement of the amygdala may only be apparent when the laughter stimulus is sufficiently emotionally involving/contagious (i.e., also depending on the stimulus intensity/duration). McGettigan, et al. 2013 finds differences in responses to passive listening to either spontaneous amusement laughter or posed laughter. Greater activity in the anterior medial prefrontal cortex in response to posed laughs was found, suggesting an obligatory attempt to determine others’ mental states when laughter was perceived as less genuine. Listening to spontaneous laughs was further associated with greater activity in bilateral superior temporal gyri. Furthermore, a greater activation of cortical motor and somatosensory regions was related to greater accuracy in distinguishing “real” from “posed” laughter, suggesting that there are sensimotor links in emotional processing that may support aspects of social understanding, see McGettigan, et al. 2013. Similarly, the researchers in Wildgruber, et al. 2013 made participants listen to posed joyful and posed tickling laughter. For the posed joy laughs, they found stronger responses in the anterior rostral mediofrontal cortex and the visual association area compared to the tickling laughter. For the tickling laughter, they found stronger responses in the auditory association cortex. They concluded that “socially complex laughter types” (i.e., laughter types beyond the reflex-like tickling laughter) are associated to areas that are concerned with mentalizing tasks and facial imagery, which may support the decoding of social intentions a laugh is related to, similarly to the findings of McGettigan, et al. 2013, which compared different “laughter types” compared to Wildgruber, et al. 2013 though.

                                                                                                                                      • McGettigan, Carolyn, Eamonn Walsh, Rosie Jessop, et al. 2013. Individual differences in laughter perception reveal roles for mentalizing and sensorimotor systems in the evaluation of emotional authenticity. Cerebral Cortex. 25:246–257.

                                                                                                                                        DOI: 10.1093/cercor/bht227Save Citation »Export Citation »E-mail Citation »

                                                                                                                                        Empirical article investigating the neural responses during passive listening to authentic amusement laughter and controlled, voluntary laughter.

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                                                                                                                                        • Meyer, Martin, Stefan Zysset, D. Yves von Cramon, and Kai Alter. 2005. Distinct fMRI responses to laughter, speech, and sounds along the human peri-sylvian cortex. Cognitive Brain Research 24:291–306.

                                                                                                                                          DOI: 10.1016/j.cogbrainres.2005.02.008Save Citation »Export Citation »E-mail Citation »

                                                                                                                                          Empirical article comparing the neural responses to hearing laughter, speech, and nonvocal sounds.

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                                                                                                                                          • Sander, Kerstin, and Henning Scheich. 2001. Auditory perception of laughing and crying activates human amygdala regardless of attentional state. Cognitive Brain Research 12:181–198.

                                                                                                                                            DOI: 10.1016/s0926–6410(01)00045–3Save Citation »Export Citation »E-mail Citation »

                                                                                                                                            Empirical article investigating in which way the amygdala, auditory cortex, and insula are involved in the processing of affective nonverbal vocalizations (laughing and crying) in healthy humans.

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                                                                                                                                            • Sander, Kerstin, and Henning Scheich. 2005. Left auditory cortex and amygdala, but right insula dominance for human laughing and crying. Journal of Cognitive Neuroscience 17:1519–1531.

                                                                                                                                              DOI: 10.1162/089892905774597227Save Citation »Export Citation »E-mail Citation »

                                                                                                                                              Empirical article investigating the question of hemispheric processing of universal (species-specific) human vocalizations that are more directly comparable to animal vocalizations.

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                                                                                                                                              • Wildgruber, Dirk, Diana P. Szameitat, Thomas Ethofer, et al. 2013. Different types of laughter modulate connectivity within distinct parts of the laughter perception network. PLoS One 8:e63441.

                                                                                                                                                DOI: 10.1371/journal.pone.0063441Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                Empirical article investigating responses to hearing different types of laughter (i.e., modulations of cerebral connectivity associated with the different laughter types) and the effects of attention shifts between implicit and explicit processing of social information conveyed by laughter.

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                                                                                                                                                Laughter and Well-Being

                                                                                                                                                “Laughing is the best medicine” is an often-heard phrase in everyday language. Martin 2001 outlines four potential models of causality for the application of laughter and humor to well-being. Moreover, Martin 2001 shows that most claims about the benefits of laughter (e.g., laughter influences endorphin levels) have to be dismissed, and no firm conclusions can be drawn from the evidence up until 2001. Furthermore, Martin 2001 shows that the lack of research in this area is partly linked to the fact that solid foundations (i.e., classifications of laughter types, etc.) and methodological rigor are often missing. Also, the direction of causality (does laughter produce well-being and good health, or do healthy individuals laugh more?) was not always addressed adequately (e.g., ruling out of alternative explanations and inclusion of control variables). Since 2001, a collection of reliable publications suggest that humor and/or laughter are at least correlated with “good health.” Pressman and Cohen 2005 elaborates on the consistent links between positive affect (PA) and physical health (e.g., trait PA and lower morbidity, state and trait PA and decreased physical symptoms and pain) in a review article (complementing the review Martin 2001, as experimental studies using comedic stimuli were also included). This evidence is in line with one possible mechanism: laughter may affect physical health indicators through the positive affective states leading to the laughter (e.g., joy, amusement). Brod, et al. 2014 reviews articles on the relationship between laughter and the immune system (including studies between 2001 and 2007). Zweyer, et al. 2004 investigates the relationship between pain tolerance (in a cold pressure test) and (1) enjoying a humorous film but inhibiting smiling and laughter, (2) smiling and laughing as much as possible and (3) producing verbal humor while watching the film. They assessed humor-related mood and facial responses of the participants and found that feeling amused was necessary for the pain reduction (but not humor production or forced laughter). While increases in pain tolerance where linked to the expression of the Duchenne display, voluntary laughter was even negatively related to pain tolerance. Nevertheless, some research reports claim harmful effects of laughter, like the triggering asthmatic fits, as reported in Liangas, et al. 2003.

                                                                                                                                                • Brod, Samuel, Lorenza Rattazzi, Giuseppa Piras, and Fulvio D’Acquisto. 2014. ‘As above, so below’: Examining the interplay between emotion and the immune system. Immunology 143:311–318.

                                                                                                                                                  DOI: 10.1111/imm.12341Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                  Review on research examining effects of emotion on the immune system. Contains a section on the effects of laughter.

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                                                                                                                                                  • Liangas, Georgios, John R. Morton, and Richard L. Henry. 2003. Mirth-triggered asthma: Is laughter really the best medicine? Pediatric Pulmonology 36:107–112.

                                                                                                                                                    DOI: 10.1002/ppul.10313Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                    Empirical article, investigating the prevalence of mirthful laughter induced asthma attacks in children.

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                                                                                                                                                    • Martin, Rod A. 2001. Humor, laughter, and physical health: Methodological issues and research findings. Psychological Bulletin 127:504–519.

                                                                                                                                                      DOI: 10.1037/0033-2909.127.4.504Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                      High-quality review on research examining effects of laughter (and humor) on physical health indicators until 2000.

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                                                                                                                                                      • Pressman, Sarah D., and Sheldon Cohen. 2005. Does positive affect influence health. Psychological Bulletin 131:925–971.

                                                                                                                                                        DOI: 10.1037/0033-2909.131.6.925Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                        Review examining the influence of state and trait positive affect on health indicators of different outcome (morbidity, mortality, survival, disease severity, physical functioning, self-reported health outcomes, physiological systems).

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                                                                                                                                                        • Zweyer, Karen, Barbara Velker, and Willibald Ruch. 2004. Do cheerfulness, exhilaration and humour production moderate pain tolerance? A FACS study. Humor: International Journal of Humor Research 17:67–84.

                                                                                                                                                          DOI: 10.1515/humr.2004.009Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                          Empirical article investigating the effect of amusement, producing humor and voluntary laughter when watching a funny film on pain tolerance in a cold pressure test, combining self-report and behavioral data.

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                                                                                                                                                          The Social Functions of Laughter

                                                                                                                                                          Laughter has different functions, from expressing emotions (both positive and negative), to inducing emotions, signaling social relationships (status, inclusion and exclusion, cohesion, mating preferences) and conversational functions (e.g., topic determination, complaints). Yet, as Owren and Amoss 2014 shows, it is difficult to tackle the different functions of laughter and grouping them. Owren and Amoss 2014 suggests classifying functions on four dimensions: benefits to vocalizer health, social status signaling, communicating vocalizer state, facilitation of social bonding. Poyatos 1993 classifies laughter types according to their function/social consequences in four basic types of situations (external versus internal and interactive versus non–interactive). In the following chapters, laughter functions are grouped in (1) emotion expression and induction aspects; (2) social facilitation; (3) social bonding, cohesion, attraction; and (4) social exclusion and status signaling.

                                                                                                                                                          • Owren, Michael J., and R. Toby Amoss. 2014. Spontaneous human laughter. In Handbook of positive emotions. Edited by M. M. Tugade, M. N. Shiota, and L. D. Kirby, 159–178. New York: Guildford.

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                                                                                                                                                            Review article elaborating on, among other topics, spontaneous (as opposed to voluntary) laughter origins, underpinnings and functions and integrating different findings.

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                                                                                                                                                            • Poyatos, Fernando. 1993. The many voices of laughter: A new audible-visual paralinguistic approach. Semiotica 93:61–82.

                                                                                                                                                              DOI: 10.1515/semi.1993.93.1-2.61Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                              Introduces a possible model for studying the audio-visual morphology of laughter, including a laughter configuration chart, and describes different laugher types and functions.

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                                                                                                                                                              Emotion Expression and Induction

                                                                                                                                                              Laughter is a behavioral marker of several emotions, positive as well as negative. Most dominantly, laughter has often been claimed to be a universal marker of joy, as Darwin 1872 described. Examining vocal features, Szameitat, et al. 2009 suggests that schadenfreude goes along with a distinct auditory laughter quality. Hawk, et al. 2009 finds that embarrassment, joy, and pride were expressed by laughter, although there were some gender differences in the acted portrayals. Controversially, Bachorowski and Owren 2001 doubts that laughter sounds could reveal specific and exclusive connections to emotional states. These researchers developed a theory on the fact that laughter was a nonverbal behavior of such enormous diversity in acoustics and production context that it may not primarily be the representation of an encoded signal but serve more to directly influence the listeners affective state and behavior through “the power of the acoustics themselves” (p. 185). As an example, they mentioned that laughers differ in their laughter utterances (i.e., voiced versus unvoiced) when watching funny films, although all participants reported positive emotions being elicited, and therefore, the laughs should be more homogeneous. Furthermore, laughter is highly contagious and can therefore foster positive affect in others through emotional contagion. Bachorowski and Owren 2001 shows the contagious effects of laughter and its capacity to elicit positive feelings, particularly for voiced laughter bouts. In Kipper and Todt 2003a, researchers modified naturally occurring laughter in different laughter series (voiced laughter samples only). They concluded that three factors in auditory laughter evaluations were important: the serial organization of laughter serving as a recognition element, the changes in acoustic parameters influencing the quality, and the accentuated elements accounting for the contagious effect of laughter. Moreover, laughter vocalizations (as well as vocalizations of negative emotions, such as crying and screams) are remembered better than neutral vocalizations, such as yawns, coughs, and sneezes, as Armony, et al. 2007 shows. Wildgruber, et al. 2013 (cited under Perception) investigates the brain responses to posed laughter types, including joyful laughter, taunt, and tickling laughter. Basing on the differential patterns of brain responses found toward those stimuli, they introduced the term of “complex social laughter types” as opposed to “reflex-like tickling laughter.” They argued that complex social laughter types serve social functions and have presumably evolved from “the unequivocal and reflex-like social bonding signal.” Bonnano, et al. 2007 shows that expressing positive emotions through Duchenne smiles and laughs promoted adjustment to aversive life events but also depended on the context of the positive emotion expression. In an applied setting.

                                                                                                                                                              • Armony, Jorge L., Caroline Chochol, Shirley Fecteau, and Pascal Belin. 2007. Laugh (or cry) and you will be remembered. Influence of emotional expression on memory for vocalizations. Psychological Science 18:1027–1029.

                                                                                                                                                                DOI: 10.1111/j.1467-9280.2007.02019.xSave Citation »Export Citation »E-mail Citation »

                                                                                                                                                                Empirical article showing a memory advantage for emotional nonlinguistic vocalizations (laughter, screams, crying), compared with neutral ones (yawning, sneezing, coughing, throat cleaning).

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                                                                                                                                                                • Bachorowski, Jo-Anne, and Michael Owren. 2001. Not all laughs are alike: Voiced but not unvoiced laughter readily elicits positive affect. Psychological Science 12:252–257.

                                                                                                                                                                  DOI: 10.1111/1467–9280.00346Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                  Empirical article investigating the perception of voiced and unvoiced samples of laughter (auditory presentation). The results show that mainly voiced laughter bouts link to perceived positive valence. A must-read for those interested in laughter decoding.

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                                                                                                                                                                  • Bachorowski, Jo-Anne, and Michael J. Owren. 2003. Sounds of emotion. Annals of the New York Academy of Sciences 1000:244–265.

                                                                                                                                                                    DOI: 10.1196/annals.1280.012Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                    Review and theory article discussing whether laughter sounds could reveal specific and exclusive associations to emotional states or whether they serve to influence the listener and the listener’s emotional state and behavior.

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                                                                                                                                                                    • Bonnano, George A., Deniz M. Colak, and Dacher Keltner, et al. 2007. Context matters: The benefits and costs of expressing positive emotion among survivors of childhood sexual abuse. Emotion 7:824–837.

                                                                                                                                                                      DOI: 10.1037/1528-3542.7.4.824Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                      Empirical article investigating the relationship between the expression of Duchenne smiles/laughs and non-Duchenne smiles and adjustment to adverse life events in groups with or without childhood abuse. Positive emotion expression was only adaptive when shown in telling memories unrelated to abuse but maladaptive when shown in telling memories of abuse.

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                                                                                                                                                                      • Darwin, Charles. 1872. The expression of the emotions in man and animals. London: John Murray.

                                                                                                                                                                        DOI: 10.1037/10001-000Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                        Absolute must read to any student interested in emotions in general and early writings on laughter. Available in free online versions in several languages.

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                                                                                                                                                                        • Hawk, Skyler T., Gerben A. van Kleef, Agneta H. Fischer, and Job van der Schalk. 2009. ‘Worth a thousand words’: Absolute and relative decoding of nonlinguistic affect vocalizations. Emotion 9:293–305.

                                                                                                                                                                          DOI: 10.1037/a0015178Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                          Empirical article on the analysis of actor encoded emotion expressions.

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                                                                                                                                                                          • Kipper, Silke, and Dietmar Todt. 2003a. Dynamic-acoustic variation causes differences in evaluations of laughter. Perceptual and Motor Skills 96:799–809.

                                                                                                                                                                            DOI: 10.2466/PMS.96.3.799–809Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                            Empirical article testing whether single laughter elements and changes in acoustic parameters, voice quality and playback order are important for the identification and evaluation of a given laugh.

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                                                                                                                                                                            • Kipper, Silke, and Dietmar Todt. 2003b. The role of rhythm and pitch in the evaluation of human laughter. Journal of Nonverbal Behavior 27:255–272.

                                                                                                                                                                              DOI: 10.1023/A:1027384817134Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                              Empirical article testing the notion that single laughter elements and changes in acoustic parameters are important for the identification and evaluation of a given laugh. Series with rhythmic patterns “long-short” and “long-short-long” (accents within the rhythm of a laughter-series) evoked more smiles and laughs in listeners than all other series.

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                                                                                                                                                                              • Szameitat, Diana P., Kai Alter, André J. Szameitat, et al. 2009. Differentiation of emotions in laughter at the behavioral level. Emotion 9:397–405.

                                                                                                                                                                                DOI: 10.1037/a0015692Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                Empirical article on emotion decoding from actor-posed laughs.

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                                                                                                                                                                                Social Facilitation

                                                                                                                                                                                It has been shown that the mere presence of a companion influences cognitive and emotional responses to amusing material. Chapman 1973 and Chapman and Chapman 1974 show that increases in a companions’ laughter increased the laughter and smiling responses, as well as ratings of funniness in participants. Later studies varied a variety of factors: the presence of a laughing versus a nonlaughing model, seating position, proximity, crowding, eye contact, age difference between subjects, and whether groups of strangers or friends were tested, same and mixed sex dyads (see Chapman 1983 for an overview, as well as Devereux and Ginsburg 2001). Several of these factors were identified as powerful in enhancing the frequency or duration of smiling and laughing. However, this effect is also observable in canned (background, dubbed) laughter, as many studies have shown, among them Fuller and Sheehy-Skeffington 1974.

                                                                                                                                                                                Cooperation, Social Bonding, Cohesion, and Attraction

                                                                                                                                                                                Chapman and Foot 1976 (cited under General Overviews, Reference Works, and Textbooks) characterizes laughter as a means of maintaining the interest and attention of the conversational partner. Since then, many studies have followed up on the notion that laughter can communicate cooperation, cohesion, and attraction and serves social bonding. Grammer 1990, as well as Grammer and Eibl–Eibesfeldt 1990, shows that laughter can signal interest in interaction partners but that the functions of laughter differ for males and females. Yet, laughter may be one feature in the creation of heterosexual relationships. Glenn 2003 (cited under General Overviews, Reference Works, and Textbooks) tackles different functions of laughter in interaction (among them the constitution of relationships and identity through laughter). Owren and Bachorowski 2001 offers an interesting theory on the functions of smiling and laughter and how different forms (i.e., spontaneous versus contrived) evolved. In short, the theory claims that smiling served as a signal for positive affect and willingness to cooperate at first; however, as it was easily fakeable, contrived smiles developed and made it harder for cooperation partners to guess whether a cooperative intent was honest or not. Thus, a more complex, less easy to fake, signal developed to signal cooperation and positive affect more securely to potential interaction partners (i.e., laughter). Although this theory offers interesting insights in the expression of spontaneous and contrived laughter, it is yet untested. Vlahovic, et al. 2012 furthermore shows that across different communication modes, laughter contributed to creating and maintaining emotionally intense social relationships. Mehu and Dunbar 2008 shows that laughter (and smiling) is likely to be involved in the formation of cooperative relationships. Dezecache and Dunbar 2012 emphasizes the bonding capacity of laughter (not only in dyads but also in larger groups) and claimed that laughter can serve “grooming” functions (i.e., “vocal grooming”). In a similar vein, Greatbatch and Clark 2003 is an ecologically valid approach to the use of humor to create audience laughter in order to form cohesion and solidarity in lectures of so-called management gurus. Kashdan, et al. 2014 elucidates that laughter not only serves important bonding functions but also increases the likelihood of future social rewards.

                                                                                                                                                                                • Dezecache, Guillaume, and Robin Dunbar. 2012. Sharing the joke: The size of natural laughter groups. Evolution and Human Behavior 33:775–779.

                                                                                                                                                                                  DOI: 10.1016/j.evolhumbehav.2012.07.002Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                  Empirical article investigating the hypothesis that laughter can serve the function of “vocal grooming.” Suitable for those with an interest in the functions of laughter and evolutionary background.

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                                                                                                                                                                                  • Grammer, Karl. 1990. Strangers meet: Laughter and nonverbal signs of interest in opposite-sex encounters. Journal of Nonverbal Behavior 14:209–236.

                                                                                                                                                                                    DOI: 10.1007/BF00989317Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                    Classic article that is a must read for every student and scholar interested in the communication of interest and attraction.

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                                                                                                                                                                                    • Grammer, Karl, and I. Eibl–Eibesfeldt. 1990. The ritualisation of laughter. In Natürlichkeit der Sprache und der Kultur. Edited by W. A. Koch, 192–214. Bochum, Germany: Brockmeyer.

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                                                                                                                                                                                      Empirical article investigating the occurrence of laughter in same-sex and mixed-sex couples and its influence on the interest of the interaction partners for one another.

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                                                                                                                                                                                      • Greatbatch, David, and Timothy Clark. 2003. Displaying group cohesiveness: Humour and laughter in the public lectures of management gurus. Human Relations 56:1515–1544.

                                                                                                                                                                                        DOI: 10.1177/00187267035612004Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                        Empirical article investigating lectures of “management gurus,” analyzing the strategies four speakers use to create audience laughter (with a particular interest in how they create cohesion and solidarity).

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                                                                                                                                                                                        • Kashdan, Todd B., Jessica Yarbro, Patrick E. McKnight, and John B. Nezlek. 2014. Laughter with someone else leads to future social rewards: Temporal change using experience sampling methodology. Personality and Individual Differences 58:15–19.

                                                                                                                                                                                          DOI: 10.1016/j.paid.2013.09.025Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                          Empirical article utilizing a diary approach to investigate the occurrence of laughter in interactions. Laughing together predicted greater intimacy, positive emotions, and enjoyment in the subsequent social interaction (and no evidence for the reverse pattern). For those interested in the positive consequences of mutual laughter.

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                                                                                                                                                                                          • Mehu, Marc, and Robin Dunbar. 2008. Naturalistic observations of smiling and laughter in human group interactions. Behaviour 145:1747–1780.

                                                                                                                                                                                            DOI: 10.1163/156853908786279619Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                            Empirical article including naturalistic observations of smiling and laughter occurring in groups. Laughter vocalizations and facial responses were coded, testing three hypotheses on smiling and laughter being involved in sexual advertisement, competition, and cooperation.

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                                                                                                                                                                                            • Owren, Michael, and Jo-Anne Bachorowski. 2001. The evolution of emotional expression: A ‘selfish–gene’ account of smiling and laughter in early hominids and humans. In Emotions: Current issues and future directions. Edited by T. J. Mayne and G. A. Bonanno, 152–191. New York: Guilford.

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                                                                                                                                                                                              Theoretical contribution hypothesizing on how smiling and laughter developed during the course of human evolution. Suitable for graduate students and researchers with background knowledge on evolutionary accounts of human development.

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                                                                                                                                                                                              • Vlahovic, Tatjana, Sam Roberts, and Robin Dunbar. 2012. Effects of duration and laughter on subjective happiness within different modes of communication. Journal of Computer-mediated Communication 17:436–450.

                                                                                                                                                                                                DOI: 10.1111/j.1083–6101.2012.01584.xSave Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                Empirical article exploring the effects of interaction duration and laughter on the rated happiness in different communication modes (e.g., face-to-face, video and normal telephone, instant messaging, texting, social network sites) in a diary study.

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                                                                                                                                                                                                Social Exclusion and Status Signaling

                                                                                                                                                                                                Mehu and Dunbar 2008 shows that laughter may also serve as a submission signal, which also differs between the two genders. Stillman, et al. 2007 shows that laughter is not only used to increase the likelihood of future rewards, but this is also dependent on the status of the person (low power versus high power). Oveis, et al. 2016 states that status influences the way people laugh (dominant versus submissive). Moreover, Mendes and Koslov 2013 shows that persons tend to exaggerate positive responses (laughter among them) toward stigmatized others (termed “overcorrection”), yet, the overcorrection can be disrupted if individuals are under stress or cognitively loaded. Platow, et al. 2005 investigates the contagious effect of canned laughter when participants were either made to believe the laughter was from in- or out-group members. Confirming the hypothesis, higher frequency and duration of laughter, as well as higher ratings of funniness were found when participants believed to hear in-group compared to out-group laughter.

                                                                                                                                                                                                • Mehu, Marc, and Robin Dunbar. 2008. Naturalistic observations of smiling and laughter in human group interactions. Behaviour 145:1747–1780.

                                                                                                                                                                                                  DOI: 10.1163/156853908786279619Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                  Empirical article including naturalistic observations of smiling and laughter occurring in groups. Laughter vocalizations and facial responses were coded, testing three hypotheses on smiling and laughter being involved in sexual advertisement, competition, and cooperation.

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                                                                                                                                                                                                  • Mendes, Wendy Berry, and Katrina Koslov. 2013. Brittle smiles: Positive biases toward stigmatized and outgroup targets. Journal of Experimental Psychology: General 142:923–933.

                                                                                                                                                                                                    DOI: 10.1037/a0029663Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                    Empirical article reporting four studies showing overcorrection (exaggerated positive responses including laughter, but also smiling, nodding, and positive statements among others) toward stigmatized individuals and how overcorrection can be disrupted.

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                                                                                                                                                                                                    • Oveis, Christopher, Aleksandr Spectre, Pamela K. Smith, Mary Y. Liu, and Dacher Keltner. 2016. Laughter conveys status. Journal of Experimental Social Psychology 65:109–115.

                                                                                                                                                                                                      DOI: 10.1016/j.jesp.2016.04.005Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                      Empirical article reporting two studies showing qualitative differences in laughter, depending on the status of the laughing person.

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                                                                                                                                                                                                      • Platow, Michael J., S. Alexander Haslam, and Amanda Both, et al. 2005. ‘It’s not funny if they’re laughing’: Self-categorization, social influence, and responses to canned laughter. Journal of Experimental Social Psychology 41:542–550.

                                                                                                                                                                                                        DOI: 10.1016/j.jesp.2004.09.005Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                        Hypothesizes that the presence or absence of canned laughter in a humorous recording and its effect is influenced by beliefs about the in-group or out-group composition of the laughing audience. Participants laughed and smiled more and longer and rated humorous material more favorably when they heard in-group laughter rather than out-group or no laughter.

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                                                                                                                                                                                                        • Stillman, Tyler F., Roy F. Baumeister, and C. Nathan DeWall. 2007. What’s so funny about not having money? The effects of power on laughter. Personality and Social Psychology Bulletin 33:1547–1558.

                                                                                                                                                                                                          DOI: 10.1177/0146167207305863Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                          Empirical article reporting two experiments that show that low-power individuals laugh more than high-power individuals in order to gain affiliation.

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                                                                                                                                                                                                          Pathological Laughter

                                                                                                                                                                                                          Many research teams have investigated the various forms of pathological laughter. This phenomenon is interesting from a clinical point of view and because of the mechanisms behind laughter in the brain. Pathological laughter (and crying) as well as emotional lability were found in patients with lesions of the brain stem and the pons (tumors in the hypothalamus), as Delalande and Fohlen 2003 shows. Parvizi, et al. 2011 investigates pathological laughter and emotional lability in hypothalamic hamartomas, and Paparrigopoulos, et al. 2010 studies their occurrence in patients with multiple sclerosis. Moreover, pathological laughter and emotional lability were also observed in Creutzfeld-Jacob disease. These lesions and illnesses (among others described in case studies) may lead to gelastic epilepsy and involuntary laughter with or without mood congruency as described in Lauterbach, et al. 2013. Frank, et al. 2012 investigates the appreciation and perception of humor, as well as facial expressions of amusement toward humorous stimuli in patients with cerebellar degeneration and healthy controls to show the differences in emotional, cognitive, and behavioral responses to humor. Laughter, with or without the component of mirth, can also be an early sign of a stroke (fou rire prodromique). Pathological laughter often occurs in inappropriate social situations and is not under the control of the person involved. Wild, et al. 2003 further shows that pathological laughter also occurs in several psychological disorders, such as mania, schizophrenia, Alzheimer’s syndrome, or genetic disorders such as the Angelman syndrome.

                                                                                                                                                                                                          • Delalande, Olivier, and Martine Fohlen. 2003. Disconnecting surgical treatment of hypothalamic hamartoma in children and adults with refractory epilepsy and proposal of a new classification. Neurologia Medico-Chirurgica 43:61–68.

                                                                                                                                                                                                            DOI: 10.2176/nmc.43.61Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                            Empirical article proposing a new anatomical classification of hamartoma (seventeen patients aged from nine months to thirty-two years).

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                                                                                                                                                                                                            • Frank, Benedikt, Björn Propson, Sophia Göricke, Heike Jacobi, Barbara Wild, and Dagmar Timmann. 2012. Humor and laughter in patients with cerebellar degeneration. The Cerebellum 11:564–573.

                                                                                                                                                                                                              DOI: 10.1007/s12311–011–0320–zSave Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                              Empirical article investigating humor appreciation, perception of humorous stimuli, and facial responses of patients with cerebellar degeneration and healthy controls.

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                                                                                                                                                                                                              • Lauterbach, Edward C., Jeffrey L. Cummings, and Preetha S. Kuppuswamy. 2013. Toward a more precise, clinically informed pathophysiology of pathological laughing and crying. Neuroscience & Biobehavioral Reviews 37:1893–1916.

                                                                                                                                                                                                                DOI: 10.1016/j.neubiorev.2013.03.002Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                                Accessible review article for students and advanced researchers.

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                                                                                                                                                                                                                • Paparrigopoulos, Thomas, Panagiotis Ferentinos, Anastasios Kouzoupis, George Koutsis, and George Papadimitriou. 2010. The neuropsychiatry of multiple sclerosis: Focus on disorders of mood, affect and behaviour. International Review of Psychiatry 22:14–21.

                                                                                                                                                                                                                  DOI: 10.3109/095402610035893Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                                  Theoretical article analyzing epidemiology, clinical features, etiology, and treatment disturbances common in multiple sclerosis.

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                                                                                                                                                                                                                  • Parvizi, Josef, Scheherazade Le, and Brett L. Foster, et al. 2011. Gelastic epilepsy and hypothalamic hamartomas: Neuroanatomical analysis of brain lesions in 100 patients. Brain 134:2960–2968.

                                                                                                                                                                                                                    DOI: 10.1093/brain/awr235Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                                    Retrospective review of clinical and structural neuroimaging data from a hundred cases of gelastic epilepsy and hypothalamic hamartoma.

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                                                                                                                                                                                                                    • Wild, Barbara, Frank A. Rodden, Wolfgang Grodd, and Willibald Ruch. 2003. Neural correlates of laughter and humor. Brain: A Journal of Neurology 126:2121–2138.

                                                                                                                                                                                                                      DOI: 10.1093/brain/awg226Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                                      Review article discussing the expression of laughter in a voluntary and involuntary neural pathway, the brain regions associated with pathological laughter, and the perception of humor.

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                                                                                                                                                                                                                      Ridicule and the Fear of Being Laughed At

                                                                                                                                                                                                                      Although laughter is commonly viewed as a positive nonverbal signal and a sign of joy, there is also evidence that laughter may be used as a sign of derision or ridicule, with important social consequences. For example, the observation of how others being ridiculed influences one’s behavior. Janes and Olsen 2000, an article on “jeer pressure,” shows the inhibiting effects of observing another person being ridiculed. Furthermore, individual differences have been identified for the (mis-) perception of the malicious/derisive intent of laughter. Gelotophobia (the fear of being laughed at) predicts the systematic misperception of laughter and laughter-related situations, as the review article Ruch, et al. 2014 outlines in its findings on gelotophobia between the publication of the first empirical article in 2008 and 2014. Gelotophobia is seen as a dimension ranging from no fear to extreme fear and has been found to be an interindividual differences variable of high stability. Individuals with a fear of being laughed at interpret laughter as a weapon for putting them down and falsely attribute it to mockery directed toward them. Consequently, gelotophobes respond aversively to laughter—independent of the laughter intent (when rating emotions toward laughter-related scenarios, when hearing different kinds of laughter, when seeing photos of laughing faces, etc.). Also, Papousek, et al. 2014 shows that gelotophobes respond with a marked heart rate deceleration when hearing laughter, which they see as a social rejection cue.

                                                                                                                                                                                                                      • Janes, Leslie M., and James M. Olsen. 2000. Jeer pressure: The behavioral effects of observing ridicule of others. Personality and Social Psychology Bulletin 26:474–485.

                                                                                                                                                                                                                        DOI: 10.1177/0146167200266006Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                                        Empirical article on the inhibiting effect of watching other people being ridiculed. Results of two experiments showed that participants who saw others being ridiculed were more conforming and more afraid of failing than were those who saw self-ridicule or no ridicule.

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                                                                                                                                                                                                                        • Papousek, Iona, Nilüfer Aydin, and Helmut Lackner, et al. 2014. Laughter as a social rejection cue: Gelotophobia and transient cardiac responses to other persons’ laughter and insult. Psychophysiology 51:1112–1121.

                                                                                                                                                                                                                          DOI: 10.1111/psyp.12259Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                                          Empirical study that combining subjective and objective data sources. The study showed that the listening to pre-recorded laughter placed in a realistic and personally relevant context led to marked heart rate deceleration in response possibly indicating a “freezing”-like response in gelotophobes.

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                                                                                                                                                                                                                          • Ruch, Willibald, Jennifer Hofmann, Tracey Platt, and René T. Proyer. 2014. The state-of-the art in gelotophobia research: A review and some theoretical extensions. Humor: International Journal of Humor Research 27:23–45.

                                                                                                                                                                                                                            DOI: 10.1515/humor-2013-0046Save Citation »Export Citation »E-mail Citation »

                                                                                                                                                                                                                            Review article that summarizes all the empirical evidence on gelotophobia after five years of empirical research. The article also provides a revised model on the causes and consequences of gelotophobia.

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