http://www.chicagotribune.com/news/local/chi-0504010071apr01,1,7102895.story?coll=chi-news-hed&ctrack=1&cset=true
Animals enjoy good laugh too, scientists say
By Peter Gorner
Tribune science reporter
Published April 1, 2005
Tickling rats to make them chirp with joy may seem frivolous as a
scientific pursuit, yet understanding laughter in animals may lead to
revolutionary treatments for emotional illness, researchers suggest.
Joy and laughter, they say, are proving not to be uniquely human traits.
Roughhousing chimpanzees emit characteristic pants of excitement, their
version of "ha-ha-ha" limited only by their anatomy and lack of breath
control, researchers contend.
Dogs have their own sound to spur other dogs to play, and recordings of
the sound can dramatically reduce stress levels in shelters and kennels,
according to the scientist who discovered it.
Even laboratory rats have been shown to chirp delightedly above the range
of human hearing when wrestling with each other or being tickled by a
keeper--the same vocalizations they make before receiving morphine or
having sex.
Studying sounds of joy may help us understand the evolution of human
emotions and the brain chemistry underlying such emotional problems as
autism and attention-deficit/hyperactivity disorders, said Jaak Panksepp,
a pioneering neuroscientist who discovered rat laughter.
Panksepp, of Bowling Green State University in Ohio, sums up the latest
studies in this week's edition of the journal Science in hopes of alerting
colleagues to results that he terms "spectacular." The research suggests
that studying animal emotions, once a scientific taboo, seems to be moving
rapidly into the mainstream.
"It's very, very difficult to find skeptics these days. The study of
animal emotions has really matured.
Things have changed completely from as recently as five years ago," said
Mark Bekoff, an expert in canine play behavior and professor of biology at
the University of Colorado, Boulder.
Biologists suggest that nature apparently considers sounds of joy
important enough to have conserved them during the evolutionary process.
"Neural circuits for laughter exist in very ancient regions of the brain,"
Panksepp said, "and ancestral forms of play and laughter existed in other
animals eons before we humans came along."
Research in this area "is just the beginning wave of the future," said
comparative ethologist Gordon Burghardt, of the University of Tennessee,
who studies the evolution of play. "It will allow us to bridge the gap
with other species."
New investigative techniques often rely on super high-tech scanning
wizardry, but the most important tool for scientists in this field is much
more simple.
"Tickles are the key," Panksepp said. "They open up a previously hidden
world."
Panksepp had studied play vocalizations in animals for years before it
occurred to him that they might be an ancestral form of laughter.
"Then I went to the lab and tickled some rats. Tickled them gently around
the nape of their necks. Wow!"
The tickling made the rats chirp happily--"as long as the animal's
friendly toward you," he said. "If not, you won't get a single chirp, just
like a child that might be suspicious of an adult."
Rats that were repeatedly tickled became socially bonded to the
researchers and would seek out tickles. The researchers also found that
rats would rather spend time with animals that chirp a lot than with those
that don't.
During human laughter, the dopamine reward circuits in the brain light up.
When researchers neurochemically tickled those same areas in rat brains,
the rats chirped.
Rat humor remains to be investigated, but if it exists, a prime component
will be slapstick, Panksepp speculated. "Young rats, in particular, have a
marvelous sense of fun."
Panksepp said that laughter, at least in response to a direct physical
stimulus such as tickling, may be a common trait shared by all mammals.
Psychologist and neuroscientist Robert Provine, author of "Laughter: A
Scientific Investigation," tickled and played with chimpanzees at the
Yerkes Regional Primate Center in Atlanta while researching the origins of
the human laugh.
Laughter in chimps, our closest genetic relatives, is associated with
rough-and-tumble play and tickling, Provine found. That came as no
surprise.
"It's like the behavior of young children," said Provine, of the
University of Maryland Baltimore County. "A tickle and laughter are the
first means of communication between a mother and her baby, so laughter
appears by about four months after birth."
The importance of such an early behavior is apparent.
"We're talking about a life-and-death deal here--the bonding and survival
of babies," Provine said.
When chimps laugh, they make unique panting sounds, ranging from barely
audible to hard grunting, with each inward and outward breath.
"We humans laugh on outward breaths. When we say `ha-ha-ha,' we're
chopping an outward breath," Provine said. "Chimps can't do that. They
make one sound per inward and outward breath. They don't have the breath
control to ... make the traditional human laugh."
The breakthrough in dog laughter was accomplished by University of Nevada,
Reno, researcher Patricia Simonet while working with undergraduates at
Sierra Nevada College in Lake Tahoe.
With extensive chimp research behind her, Simonet was open to the idea of
animal emotions, but the laughing sound she discovered in dogs was
unexpected: a "breathy, pronounced, forced exhalation" that sounds to the
untrained ear like a normal dog pant.
But a spectrograph showed a burst of frequencies, some beyond human
hearing. A plain pant is simpler, limited to just a few frequencies.
Hearing a tape of the dog laugh made single animals take up toys and play
by themselves, Simonet said. It never initiated aggressive responses.
"If you want to invite your dog to play using the dog laugh, say `hee,
hee, hee' without pronouncing the `ee,'" Simonet said. "Force out the air
in a burst, as if you're receiving the Heimlich maneuver."
When she played a recording of a laughing dog at an animal shelter,
Simonet found that even 8-week-old puppies reacted by starting to play,
something they hadn't done when exposed to other dog sounds.
"Some sounds, like growls, confused the puppies. But the dog laugh caused
sheer joy and brought down the stress levels in the shelter immediately."