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Animal behavior - the rat that laughed / Jesse Bering

Are there animals with a sense of humor besides humans? Maybe

Once, while drowsy and engrossed in a blur of heights somewhere about seven miles above Iceland, I distractedly felt the warm blue blanket peeking out from under my seat, then noticed, to my dismay, that I was tugging hard on a big, wriggling toe covered in a thick sock. With a temper like mine, life tends to roll from one awkward conversation to another, but as I turned back with a smile to apologize to the owner of the toe, my gaze met a particularly large man whose scowl indicated that he had trouble seeing the humor in this incident.

Unpleasant, of course, but now I see this random event as the beginning of an unexpected discovery. As I rested my head again on the pillow covered in the disposable airline cover, my hazy mind flew to a far more pleasant memory related to another big toe that belonged to an animal far more good-humored than the one sitting behind me. This other toe, which was just as thick and clumsy to the touch as its human counterpart, I should note, was attached to King, a male gorilla of the western lowland gorilla subspecies. King weighed about 200 kilograms and suffered from calcification of the gums. In the summer of 1996, when I was 20 and he was 27, I spent considerable time with my friend Toothless King listening to Frank Sinatra and the Three Tenors while playing catch while tickling his toe. He would lean back on his nightstand, reach out to me through the bars of the cage with a huge ash-colored foot and let it sway slightly in anticipation; And when I would grab one of his toes and give it a good squeeze he would burst out with guttural roars of laughter shaking his shoulders. King was almost unable to control himself when I snuck down one day and pretended to bite the chubby finger. If you have never seen a gorilla in a laughing fit, I encourage you to go out and seek out such a spectacle before your life ends. The sight will cause cognitive dissonance even in the mind of the most ardent creationist.

Are there any animals endowed with a sense of humor besides humans? Maybe, in some ways. But in other ways it is likely that humans have unique qualities associated with such emotions. Aside from anecdotal stories, we know very little about the laughter and humor of other apes, but some of the most important findings to emerge from comparative behavioral science over the past decade include the unexpected discovery that rats, and especially young rats, laugh. Yes, you read that right: rats laugh. At least this is the stubborn argument put forward by the researcher Jak Panksepp, who published an impressive and rather enthusiastic position paper on the subject in the journal Behavioral Brain Research.

Funksp's research focused mainly "on the possibility that the animals we use most often in our studies, the rodents kept in laboratories, can experience a kind of social joy during their playful activity, and an important communicative-emotional component of this process, which strengthens social attachment, is an ancient form of laughter .” wait Before you start imagining giggles like those of animated movie star Stuart Little (wait, he wasn't a mouse?), consider that a real rat's laugh is unlikely to sound like a human's, involving short bursts of sound that begin with loud, complex gasps A series of short and clear pulsating movements separated from each other by almost identical time intervals. The characteristic sound of human laughter is a blowing sound as in the pronunciation of the letter "a" followed by an open movement (ie a sound similar to "ha ha ha") and is rich in harmonies because of the structure of our throat and voice box. In contrast, a rat's laughter appears in the form of high-frequency ultrasonic calls of 50 kHz, or "chirps", which are distinctly different from other sounds that rats make. And this is how Funksp describes the way he discovered the phenomenon:

Immediately after completing the first formal (i.e., well-controlled) behavioral analysis of human grappling games in the late 90s, in which laughter was a very common response, I had the "insight" (and perhaps an illusion) that the chirping response at a frequency of 20 The kilohertz of playing rats may have some ancient connection to human laughter. The next morning I came to the lab and asked my then young research assistant to come and tickle some rats.

In the years that followed, Funksp and his research assistants conducted many systematic studies on the laughter of rats and discovered a fascinating overlap between the functional and expressive characteristics of the chirping response in young rodents and the laughter of young human children. To induce laughter in his rat pups, Funksp used a method he called "heterospecific sleight of hand", a professional term for ordinary tickling.

Rats seem to be particularly sensitive to tickling in the nape of their neck, which is also the organ where the young focus their play activities, such as pinning behavior (where one rat pins the other with its back to the ground). Funksp soon found that the rats most sensitive to tickling, that is, those that experimentally emitted the most stable and reliable 50-kHz chirps when held by humans, were also the individuals that showed a stronger natural tendency to play than the others. He also found that young rats' laughter encouraged bonding: rats that had been tickled actively sought out the hands of people who had previously made them laugh. On top of that, and as we would expect from humans, certain negative environmental stimuli sharply reduced the incidence of laughter among the rodents being tested. For example, the laughter chirps were significantly reduced, even when the laughter stimulus was given regularly, when the rat pups smelled a whiff of cat, when they were very hungry, or when they were exposed to unpleasantly bright lights while being tickled. Funksp further discovered that adult females were more receptive to tickling than males, but in general it was difficult to induce tickling in adult animals, "unless they were tickled a lot when they were young." And finally, when young pups were given a choice between two different adults, one that still chirped a lot and one that didn't, they spent a much longer time in the company of the apparently happier adult rat.

Perhaps it is not surprising that Fanksp encountered disappointing resistance to his interpretation of this body of findings, particularly among his fellow scientists. And yet he insists on claiming:

I tried to deny our view time and time again, and failed to do so. We therefore believe that we are right to cautiously advance, and nurture in experimental ways, the theoretical possibility that there is some kind of ancient connection between the play chirps of young rats and the laughter of human infants.

Funksp is the first to admit that his findings are not a hint that rats have a "sense of humor", but only that there is probably an evolutionary continuity between vocal expressions in young rats and the laughter of children in wrestling games. A sense of humor, and especially the humor of adults, requires cognitive mechanisms that may or may not be found in other biological species. But he nevertheless raises the idea that this question can be experimentally disproved: "If a cat... is a constant bothersome feature in the life of a rat, would that rat make a few squeals of joy if something bad happened to its enemy? Would a rat chirp if the cat was caught in a trap or caught by the end of its tail and disappeared into thin air? We would not recommend conducting such cruel experiments, but we would encourage anyone who aspires to go in this direction to find more moderate ways of measuring these issues.”

Differences between laughter "systems" among mammals are reflected in the differences found between biological species in certain areas of the brain and in the structure of the organs that produce sounds. In the same issue of the Journal of Behavioral Brain Research, neurophysiologist Martin Mayer and his colleagues describe these differences in great detail. Although brain imaging studies of people who watched funny cartoons or listened to jokes reveal the activation of evolutionarily ancient structures such as the amygdala and the nucleus accumbens, it became clear that later "higher order" structures in brain development are also activated, including scattered areas of the cerebral cortex the front. Thus, although non-human apes laugh, human humor apparently involves highly specialized cognitive networks, which are not found in other biological species.

Laughter in our biological species is of course triggered by a wide range of social stimuli and occurs in many emotional contexts, not all of which are positive. For example, we will mention a few emotional contexts that accompany bursts of laughter, including joy, affection, amusement, gaiety, surprise, nervousness, sadness, fear, shame, aggression, a sense of victory, teasing and joy. Usually laughter serves as an emotionally charged social signal and occurs in the presence of others. This prompted psychologist Diana Schmitt and her team to investigate the possibility that human laughter has an adaptive role. Their research, published in the journal Emotion, provides the first experimental evidence that humans are equipped with a surprising ability to identify the psychological intent of a laughing person, based on the phonetic qualities of the laughter sounds alone. And sometimes, the researchers point out, laughter signals extremely violent intentions, a fact that may promote, from an evolutionary point of view, appropriate behavioral responses or have adaptive biological value on the part of the listener.

Inducing real, well-differentiated emotions under controlled laboratory conditions is a very difficult, if not impossible, task. Therefore, in their first study, Schmidt and her colleagues chose the best way possible: they hired eight professional actors (three men and five women) and recorded their laughter. This is not ideal, of course, and the researchers admit that the application of findings obtained from "displaying emotions" is limited from the start compared to using real emotions. But "the actors were instructed to focus only on the experience of the emotional state and not at all on its outward expression through laughter." Here are the four basic types of laughter that the actors were asked to display along with examples of descriptions and scenarios designed to help the actors get into the characters in the roles they played:

Laughter full of joy: meeting a good friend after not seeing each other for a very long time.

A teasing laugh: Laugh at an opponent's expense after defeating them. It reflects a feeling of contempt for mockers and is intended to humiliate the listener.

Laughter of joy to Id: laughing at a person who had an unpleasant incident, such as slipping on dog feces. Unlike teasing laughter, this laughter is not intended to really hurt the other person.

Tickling laughter: Laughter of a person being tickled, literally.

After the recordings were collected, 72 English-speaking participants were invited to the laboratory, where they were given headphones and asked to identify the emotions behind the various laughter recordings. The people listened to lots of laughter clips: 429 laughter tracks in total, each representing bursts of laughter at random intervals of three to nine seconds in length, meaning there were between 102 and 111 laugh clips for each emotion. (The task took about an hour, a nightmare-inducing thought that reminds me of the sitcoms from the 80s, which focused my attention on the bursts of laughter recorded in the background.) But the findings were impressive: the participants were able to correctly classify the laughter tracks, according to the emotions implicitly expressed in them, with a high probability It is to be expected when the identification is purely coincidental.

In a second study, the procedure was almost the same, but the participants were asked a series of other questions, relating to social dynamics. For each recording track, they were asked if the "addressee" (that is, the laugher) was in an excited or relaxed physical state; if he was dominant or submissive compared to the "recipient" (that is, the object of his laughter); whether he was in a pleasant or unpleasant state; And if he was friendly or aggressive towards the recipient. In this study there were no "right" or "wrong" answers, because distinguishing these characteristics of the laughter strips involved their subjective attribution. And yet, as expected, each category of laughter (joy, teasing, joy to Id, tickling) had its own unique profile on these four social dimensions. This means that the participants used these sounds as a reliable basis for receiving certain social information about a situation they did not see with their own eyes. The responses to joy, for example, were of low arousal, submission and positive valence regarding both parties (addressee and recipient). Teasing laughter stood out in particular: it was very dominant and was also the only sound that the participants perceived as having a negative valence directed towards the recipient.


The participants' perception of Simcha Laid's laughter was particularly interesting. It sounded dominant to them, but not to the extent of teasing laughter: subjects who made such a laugh were judged to be in a more positive state than those who were teased and less so than those who laughed a tickle laugh. Laughter of joy to Eid does not sound aggressive towards the recipient nor friendly towards him, but neutral. In the opinion of the authors, their interpretation of these data was influenced by evolutionary logic: "Laughter of Simcha Laid may represent a precise (and socially tolerated) tool to control the listener without at the same time causing him to be removed from the group context."

Credit: Wikipedia, Inge Habex
Credit: Wikipedia, Inge Habex

I'd like to think I'm witnessing pure pure joy on King's part in those years in the distant past, but clearly my brain isn't built to decipher the distinct emotional states of gorillas. Since then he has apparently been laughing at Ellen DeGeneres while watching her on TV in his cage. A sample of two is too small, I know, but maybe he thinks gay people are especially funny [DeGeneres and the author of the article "come out" publicly - the editors]. Anyway, I'm happy to think about the evolution of Simcha. And I have to say this too, this data on rats made me seriously consider returning to my vegetarian days - not because I eat rats, of course, but because laughing animals especially illustrate to me the possibility of suffering animals. If only dead cows weren't such a wonderful delicacy.


Adapted from the book: "Why is this the shape of the penis?... and other reflections on being human", by Jesse Bering, in an agreement between Scientific American and the book publishers Farrer, Strauss and Giraud (North America), Transworld (UK), Jorge Zahara Editora (Brazil). All rights reserved © 2012 by Jess Bering.

About the author

Jesse Bering (Bering) is a regular contributor to Scientific American, State magazine and Das Magazin (Switzerland). Bering headed the Institute for Cognition and Culture at Queen's University in Belfast, Northern Ireland. He lives near the city of Ithaca in the state of New York.

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