From the BBC's Science and Techonology webpage http://news.bbc.co.uk/hi/english/sci/tech/ Friday, May 1, 1998 Published at 18:22 GMT 19:22 UK Sci/Tech Rats 'like a laugh' It is not known if rat jokes exist Scientists say giggling, ticklish rats have provided them with the first credible evidence that animals unrelated to humans can laugh. For years biologists have known that chimpanzees and even some monkeys produce a panting noise akin to human laughter. But there is scant evidence that other animals are capable of laughter. Now two American scientists are claiming to have discovered that rats "laugh" when tickled. Inaudible to humans Rat laughter is not the same as humans, however. It consists of high-pitched, chirping whistles, outside the range of human hearing. The noises have been detected before but were previously believed to signal distress, aggression, or sexual excitement. Jaak Panksepp and Jeffrey Burgdorf, of Bowling Green State University in Ohio, found that young rats chirp vigorously during rough-and-tumble play sessions. They also chirped more than their older relatives when tickled. According to the scientists, this fits in with the idea that children are more ticklish than adults. Tickling experiments Mr Panksepp and Mr Burgdorf believe the tickling experiments show that a "primal form of laughter" evolved well before primates appeared. They suggest that both rats and primates use laughter to distinguish playful from threatening physical behaviour. Mr Panksepp told New Scientist magazine: "We'd be surprised if rats have a sense of humour, but they clearly have a sense of fun." A laughter expert from the University of Maryland, Baltimore, Robert Provine, believed many social mammals probably produced laughter-like sounds. But he told New Scientist it took an "intuitive leap" to recognise the calls as laughter, because the sounds were very different. ---------------------------------------------------------------------- From the New Scientist Magazine (On the web at http://www.newscientist.com/) dated 2nd May, Page 14. http://www.newscientist.com/ns/980502/nlaugh.html Primal mirth is no laughing matter By David Concar heard the one about the giggling lab rat? Psychologists in the US claim to have the first credible evidence that animals other than humans and our close cousins are capable of laughter. For years, biologists have known that chimpanzees and even some monkeys produce a panting sound akin to human laughter, but evidence of mirth among other mammals has been vague and anecdotal. Jaak Panksepp and Jeffrey Burgdorf of Bowling Green State University in Ohio tried to rectify the situation - by tickling rats. Rats respond to tickling by emitting ultrasonic whistles outside the range of human hearing. These rodent chirpings have been detected before, but most researchers believe they signalled distress or agression, or were a prelude to sex. The researchers found that young rats chirp vigorously during rough-and-tumble play sessions with each other. They also chirp more than their older relatives when they are tickled, which Panksepp says fits with the idea that children are more ticklish than adults. Panksepp believes the tickling experiments show that a "primal form of laughter" evolved well before primates appeared. He suggests that rats and primates, especially juveniles, use laughter to distinguish play from threatening physical interactions. "We'd be surprised if rats have a sense of humour, but they clearly have a sense of fun," he says. Panksepp expects many scientists to be sceptical about claims for human emotions in a lower species, but he points out that out laughter is triggered by evolutionarily ancient brain regions - its not exactly a cerebral activity. Robert Provine, who studies laughter at the University of Maryland, Baltimore County, believes many social mammals probably produce laughter-like sounds. But he admits it takes "an intuitive leap" to recognise the calls as laughter, because they are acoustically very different. ---------------------------------------------------------------------- AP story (from the CNN web page http://www.cnn.com): Rats tickled pink with new rodent laughter research The Associated Press BOWLING GREEN, Ohio 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." ---------------------------------------------------------------------- Panksepp paper: TITLE: Anticipation of play elicits high-frequency ultrasonic vocalizations in young rats. SOURCE: Journal of Comparative Psychology; Vol 112(1) Mar 1998 65-73 AUTHOR(S): Knutson, Brian; Burgdorf, Jeffrey; Panksepp, Jaak AFFILIATION: National Insts of Health, National Inst on Alcohol Abuse & Alcoholism, Lab of Clinical Sciences, Bethesda, MD, USA MAJOR SUBJECTS: Animal Play; Animal Social Behavior; Animal Vocalizations; Appetite; Motivation MINOR SUBJECTS: Infants (Animal); Rats KEY PHRASE: frequency ultrasonic vocalizations, juvenile rats 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.