“It is not known if rat jokes exist.”

Rats Tickled Pink / May 3, 1998

“Rats just want to have fun. The fact that rats can laugh, and do, is nothing new to scientists, but a researcher at Bowling Green State University found that the rodents most people consider filthy pests are also playful — and love to be tickled. “About a year ago, I literally came into the lab one morning and said, ‘Let’s go tickle some rats,”‘ said Jaak Panksepp, a psychobiologist. “As soon as we did it, it was ‘Eureka!’ This vocalization came on right away, and more intense than before. And the data have literally been flowing ever since.” A graduate student came up with the idea of recording the giggling rats by using “bat detectors,” sophisticated instruments that register high-pitched sounds humans cannot hear. “Lo and behold … it sounded like a playground,” Panksepp said, adding that keeping rats laughing isn’t difficult. “It’s quite easy. They’re small, of course, but it’s really no different than running your fingers as if you’re tickling a child,” he said. “You get the most laughter at the nape of the neck, where they direct each other’s play behavior.” Rats register their gratitude with little nips. “I have literally tickled hundreds of rats,” Panksepp said. “The amazing thing is, prior to starting this line of research, I had never been bitten by a rat. But since I’ve started this, I’ve been bitten hundreds, if not thousands, of times, but always in a playful way. “The skin has never been broken. It’s like a puppy dog biting you.” Panksepp knows people may laugh at his research, but he doesn’t care since his goal is to track the biological origins of joy. “We interpret this as a primitive, childlike joyfulness,” he said. “Where do we humans get more laughter than anywhere else? On the playground, where kids are running and playing. It’s the same with tickled rats.”

Anticipation of play elicits high-frequency ultrasonic
vocalizations in young rats / Mar 1998
Knutson, Brian; Burgdorf, Jeffrey; Panksepp, Jaak

ABSTRACT: The authors provide initial documentation that juvenile rats emit short, high-frequency ultrasonic vocalizations (high USVs, ½55 kHz) during rough-and-tumble play. In an observational study, they further observe that these vocalizations both correlate with and predict appetitive components of the play behavioral repertoire. Additional experiments characterized eliciting conditions for high USVs. Without prior play exposure, rats separated by a screen vocalized less than playing rats, but after only 1 play session, separated rats vocalized more than playing rats. This finding suggested that high USVs were linked to a motivational state rather than specific play behaviors or general activity. Furthermore, individual rats vocalized more in a chamber associated with play than in a habituated control chamber. Finally, congruent and incongruent motivational manipulations modulated vocalization expression. Although play deprivation enhanced high USVs, an arousing but aversive stimulus (bright light) reduced them. Taken together, these findings suggest that high USVs may index an appetitive motivation to play in juvenile rats.


“As Jaak Panksepp, the neuroscientist who first discovered rat laughter, has pointed out: ‘Every drug used to treat emotional and psychiatric disorders in humans was first developed and found effective in animals. This kind of research would obviously have no value if animals were incapable of experiencing these emotional states.'”

“It has only been in the last 60 years or so that the modern science of human personality began to emerge, a system of assessing distinct personality traits that has its roots in World War II, when the U.S. government assigned to the Office of Strategic Services (the forerunner of today’s C.I.A.) the task of identifying which individuals had the right traits to be spies. A number of different personality-mapping methods and traits-assessment tests have been developed over the years, all of them pivoting around the principle that certain traits can be consistently observed in individuals across time and different situations. The most widely applied test today uses the categories defined by what is known as the Five-Factor Model (F.F.M.): openness, conscientiousness, extroversion, agreeableness and neuroticism.” Gosling then reviewed 19 different previous behavioral studies of nonhuman species through the same F.F.M. framework and found a similar recurrence of those dimensions across a surprisingly broad spectrum of species. Among the traits remarked upon were such things as “opportunistic, self-serving” behavior in certain vervet monkeys; “emotionality” in rats; “fear avoidance” in some guppies and “extroversion” in others; and, in Anderson and Mather’s 1993 paper, both “boldness” and “avoidance” in octopuses. “The evolutionary continuity between humans and other animals suggests that some dimensions of personality may be common across a wide range of species,” Gosling wrote in the resulting paper he published in 1999 in the journal Current Directions in Psychological Science. “Scientists have been reluctant to ascribe personality traits, emotion and cognitions to animals, even though they readily accept that the anatomy and physiology of humans is similar to that of animals. Yet there is nothing in evolutionary theory to suggest that only physical traits are subject to selection pressures.”

Indeed, animals like dogs and cats point up what often appears to be a paradoxically prodigious “duh factor” behind this otherwise cutting-edge science. While scientists may tussle endlessly over the validity of applying the word personality to nonhumans, for people in the everyday world – especially those who spend any time around animals – the assertion that they have distinct personalities seems absurdly obvious. At one point in his Austin office on the afternoon I met with him, Sam Gosling pulled from his shelves the 1935 edition of “A Handbook of Social Psychology,” a standard human psychology textbook
of the time, and showed me the table of contents. More than a quarter of the textbook’s chapters were devoted to studies of animals and other life forms, titles like “Population Behavior of Bacteria,” “Insect Societies” or “The Behavior of Mammalian Herds and Packs.” There is even a chapter devoted to “Social Origins and Processes Among Plants.” But in the 1954 edition of a similar work called “The Handbook of Social Psychology,” there is but one chapter devoted to nonhuman research. Titled “The Social Significance of Animal Studies,” it is essentially a desperate last plea to social psychologists not to abandon animal studies, arguing at one point that “social psychology must be dangerously myopic if it restricts itself to human literature.” The warning clearly went unheeded. The most recent edition of the handbook, from 1998, is devoted entirely to humans. “The great and enduring contribution of behaviorism,” Gosling says, “is that it introduced the scientific method to the study of behavior. They said, ‘Let’s get rid of the fuzzy, sentimental higher-level descriptions.’ And they did. They went to great efforts to record specific behaviors, things like how many times a chimpanzee scratched its head or nose. But it’s hard to study higher-order phenomena, things like personality and emotion, in just those ways. In the end, what you’re left with is this long catalog of meaningless descriptions. If I need to know whether I can go into that cage or not to clean it, it’s not useful to tell me the chimp scratched its nose 50,000 times in the past year. Just tell me, Is it aggressive or not?”

When we did our free-range fly experiments, we marked them individually. We put little colored paint dots on their thorax. The students loved it. They’d say: ‘You know Blue? He’s been attacking everyone this morning. He’s on Banana A, and everyone else is on Banana B. He’s the ruler of Banana A.’ Of course, the other thing we’ve noticed is that individuals that behave like Blue get into trouble because, you see, they end up with nobody to mate with.” Roland Anderson sees the diversity of temperaments as a manifestation of that most basic biological imperative of survival, an array of personality traits being kept in play in a given species because of the differing, shifting environmental circumstances that groups may encounter. “What happens,” he asked, “if a big school of herring comes along and eats all the aggressive, fearless males in a group of smaller fish? Well, there will still be some of the more passive or shy ones hiding under that rock that can say: ‘Hey, they’re all gone now. There’s a nice-looking female over there. I think I’ll reproduce with her.”‘ Andy Sih, like most of his colleagues at Davis, views personality differences in animals in a Darwinian context. He considers specific behaviors and preferences from an evolutionary perspective and tries to determine how various traits affect the long-term survival of a given species. And in the course of his research on everything from water striders to salamanders, Sih has become fairly obsessed with what he calls “stupid behaviors,” ones that don’t seem to make any evolutionary sense whatsoever. “You’d expect animals to be doing smart stuff,” Sih told me one evening over dinner. “The whole tradition in most of evolutionary ecology has been to emphasize adaptation where organisms do smart things. But I’ve been making the case for a while that the most interesting behaviors are actually the stupidest.”

Leave a Reply