Animals love to play, as any pet owner knows, but laughing appears to be reserved for humans, a few apes, and maybe a few birds who can mimic people and apes. Laughter has been “recorded in at least 65 species,” according to a recent study published in the journal Bioacoustics, reports Jessica Wolf at UCLA Newsroom. “Primates, domestic cows and dogs, foxes, seals, and mongooses, as well as three bird species, including parakeets and Australian magpies, are all on the list.” This is a huge cry from only a few years ago, when apes and rats were the “only known creatures to get the giggles,” as National Geographic’s Liz Langley put it in 2015.
Rats do, in fact, laugh. What evidence do scientists have for this? Of course, they tickle them, as you can see in the video above. (It turns out that tickling rats is beneficial to their health.) The goal of this study was to learn more about human contact, and tickling is “one of the most poorly known types of touch,” according to study author Michael Brecht.
Laughter, on the other hand, appears to be more universally understood, even among species separated by millions of years of evolution. Sasha Winkler, a UCLA primatologist, and Greg Bryant, a UCLA professor of communication, describe how “play vocalizations” convey non-aggression during roughhousing in a recent publication. Winkler expresses it thus way:
When we laugh, we are typically informing people that we are having a good time and asking them to join us. According to some researchers, this type of vocal activity is common among many animals who play, and that laughing is our human equivalent of an evolutionarily old vocal play signal.
Humans, on the whole, are unlikely to recognize or even notice animal laughing as such. The authors state, “Our research reveals that vocal play cues are frequently subtle.” Rats, for example, produce “ultrasonic vocalizations” that are audible to humans. Chimpanzees’ play vocalizations, on the other hand, are far more akin to human laughing, “although there are some variances,” according to Winkler. “They vocalize on both the in-breath and out-breath, for example.”
What is the point of studying animal laughter? Beyond the topic’s obvious appeal — which is particularly appealing to scientists — there’s the serious task of figuring out how “human social complexity allowed laughter to develop from a play-specific vocalization into a sophisticated pragmatic signal,” as Winkler and Bryant put it. We use laughing to convey a variety of messages, not all of which are amusing. But, no matter how many applications humans discover for the vocal signal, we can see how deeply non-aggressive play is woven across the animal world and in our evolutionary past in this new review paper. Here’s a link to a paper called “Play vocalizations and human laughter: a comparative evaluation.”