Laughter Among Humans and Nonhumans

“Laughter is the shortest distance between two people,” Victor Borge once said. As a good Darwinist, I enjoy finding proof that humans are not that different from other life forms. We share many characteristics with the other living creatures with whom we share our planet. Laughter is one more example.

Laughing is an involuntary reaction in humans consisting of rhythmical contractions of the diaphragm and other parts of the respiratory system. External stimuli, like being tickled, mostly elicit it. We associate it primarily with joy, happiness, and relief, but fear, nervousness, and embarrassment may also cause it. Laughter depends on early learning and cultural factors.

The study of humor and laughter is called gelotology (from the Greek gelos, γέλιο, meaning laughter). Laughter as communication is found in over 60 species (Johnson 2021).

Chimpanzees, gorillas, bonobos, and orangutans display laughter-like behavior when wrestling, playing or tickling. Their laughter consists of alternating inhalations and exhalations that sound to us like breathing and panting. It’s possible that the variations in human and chimpanzee laughter are the result of modifications that have evolved to make speech possible. It seems the tickling sounds emitted by bonobos and newborn humans followed the same sonographic pattern even though they had a higher frequency. The armpits and belly are two parts of the body that both humans and chimps find itchy.

Researchers found that when tickled, humans and apes (chimpanzees, bonobos, gorillas, and orangutans) laugh in comparable ways. That suggests laughing originated among primate species and before the origins of humans. Researchers gathered recordings of playfighting vocalizations across primate species, and by comparing the sounds to our own laughter, they were able to create an evolutionary tree dating back 60 million years (Davila Ross et al 2009).

Rats display extended, high frequency, 50 kHz ultrasonic vocalizations during play and when tickled. We can only hear these chirping sounds with proper equipment. The most giggling rats also play the most and prefer to hang around with other giggling rats more. They are also ticklish, as are we. Particular areas of their body are more sensitive than others. There is an association between laughter and pleasant feelings. Social bonding occurs with the human tickler, and the rats can even become conditioned to seek the tickling (Paredes-Ramos et al 2012; Wöhr and Schwarting 2007;Panksepp and Burgdorf, J. 2003).

Researchers studying dolphins became aware of a particular combination of sounds composed of a whistle and a brief pulse burst. Further observations led the researchers to the conclusion that dolphins only made these signals during playfighting and never during serious fighting. They came to the conclusion that the dolphins were making these noises to signal that the situation was amicable and non-threatening and to help prevent it from worsening into something akin to an actual fight. According to these researchers, this is the reason why this laughter behavior existed in the first place. They hypothesized that these pacifying noises were the dolphin equivalent of human chuckles (http://www.dolphincommunicationproject.org).

A dog’s laughter sounds similar to a regular pant. A sonograph analysis of this panting behavior shows that the variation of the bursts of frequencies is comparable with the laughing sound. When we play this recorded dog-laughter to dogs in a shelter, it can contribute to promoting play, social behavior, and decrease stress levels (Simonet, at al 2005).

“Laughter is the shortest distance between two people.” Perhaps, when available, it is simply the shortest distance between any two living creatures.

References

Johnson, D. (2021). “From apes to birds, there are 65 animal species that “laugh”.“ Ars Technica. Retrieved 20 May 2021.

Panksepp & Burgdorf, 2003, Laughing rats and the evolutionary antecedents of human joy?  Physiology & Behavior. 79 (3): 533–547. doi:10.1016/s0031-9384(03)00159-8. PMID 12954448. S2CID 14063615.

Paredes-Ramos, P.; Miquel, M.; Manzo, J.; Pfaus, J.G.; López-Meraz, M.L.; Coria-Avila, G.A. (2012). “Tickling in juvenile but not adult female rats conditions sexual partner preference”. Physiology & Behavior. 107 (1): 17–25. doi:10.1016/j.physbeh.2012.05.017. PMID 22640704. S2CID 161288.

Davila Ross, M., J. Owren, M., Zimmermann, E. (2009). “Reconstructing the Evolution of Laughter in Great Apes and Humans”. Current Biology. 19 (13): 1106–1111. doi:10.1016/j.cub.2009.05.028. PMID 19500987. S2CID 17892549.

Simonet, P.; Versteeg, D. & Storie, D. (2005). “Dog-laughter: Recorded playback reduces stress related behavior in shelter dogs” (PDF). Proceedings of the 7th International Conference on Environmental Enrichment.

Wöhr, M.; Schwarting, R.K. (2007). “Ultrasonic communication in rats: Can playback of 50-kHz calls induce approach behavior?”. PLOS ONE. 2 (12): e1365. Bibcode:2007PLoSO…2.1365W. doi:10.1371/journal.pone.0001365. PMC 2137933. PMID 18159248.

Featured image: Laughter is common among humans and 62 nonhumans species (photos by unknown; composition by R. Abrantes).