by Kevin Schofield

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This weekend’s read is a fascinating research paper by two UCLA professors looking at the vocalizations animals make when they are at play. It’s been well documented that many species of animals, and especially mammals, play. Play serves an important role: it allows animals to practice skills from basic coordination to chasing and fighting; it also facilitates bonding within members of a family.

Researchers have also studied the variety of sounds that animals make, including when they are threatened as well as when they are playing. Vocalizations are also important in that they facilitate play interactions: they can signal the desire to play and the intent for chasing and play-fighting to be non-threatening, and they can also limit the costs and risks of play by communicating pain or a need for the play session to end. 

Play vocalizations are usually quiet so that players can communicate among themselves without the risk of attracting predators. Larger-bodied animals such as dogs, elephants, and humans are sometimes exceptions to this rule since they are less vulnerable to predation.

The researchers assembled data from other studies on the play vocalizations that 65 different species make in order to look for commonalities. Following a well-known theme that for animal vocalizations the form tends to follow its function (for example, alarm sounds that attract attention and are difficult to ignore),  they found that many species’ play vocalizations resemble panting or labored breathing: a signal to an animal’s physical stamina and often compared to humans’ laughing.  In fact, the researchers discovered that all of the species of great apes (including humans) that exhibit this kind of panting-style play vocalization trace back to the same common ancestor that lived about eighteen million years ago.

The most fascinating part of the research paper, however, is its discussion of what this tells us about human laughter. While it can serve the same purpose for people that it does in animals, we have also evolved it into a multi-purpose vocalization: it can be spontaneous when we are tickled or hear a funny joke, and it’s also a contagious group-bonding or “group chorus” activity (think about kids on a playground or the audience in a stand-up comedy show). But laughter is also a critical element of how we communicate nuance and context when we speak in ambiguous terms. The researchers point to studies that show that speakers laugh more than listeners do; laughter often sets context and expectations for what we’re about to say, whether it’s a funny story or whether we’re taunting someone. As with animals at play, it’s usually a sign that our presence and actions are not serious or threatening.

Do animals laugh? Perhaps; but not for all of the reasons that we humans do.

Play vocalisations and human laughter: a comparative review

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📸 Featured Image: Photo by Ian Dyball/Shutterstock.com.

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