- 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.
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- Joy and laughter, they say, are proving not to be uniquely
human traits.
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- 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.
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- 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.
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- 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.
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- 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.
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- 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.
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- "It's very, very difficult to find skeptics these
days. The study of animal emotions has really matured.
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- 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.
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- Biologists suggest that nature apparently considers sounds
of joy important enough to have conserved them during the evolutionary
process.
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- "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."
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- 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."
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- 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.
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- "Tickles are the key," Panksepp said. "They
open up a previously hidden world."
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- Panksepp had studied play vocalizations in animals for
years before it occurred to him that they might be an ancestral form of
laughter.
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- "Then I went to the lab and tickled some rats. Tickled
them gently around the nape of their necks. Wow!"
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- 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."
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- 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.
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- 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.
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- 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."
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- 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.
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- 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.
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- Laughter in chimps, our closest genetic relatives, is
associated with rough-and-tumble play and tickling, Provine found. That
came as no surprise.
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- "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."
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- The importance of such an early behavior is apparent.
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- "We're talking about a life-and-death deal here--the
bonding and survival of babies," Provine said.
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- When chimps laugh, they make unique panting sounds, ranging
from barely audible to hard grunting, with each inward and outward breath.
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- "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."
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- 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.
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- 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.
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- But a spectrograph showed a burst of frequencies, some
beyond human hearing. A plain pant is simpler, limited to just a few frequencies.
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- Hearing a tape of the dog laugh made single animals take
up toys and play by themselves, Simonet said. It never initiated aggressive
responses.
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- "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."
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- 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.
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- "Some sounds, like growls, confused the puppies.
But the dog laugh caused sheer joy and brought down the stress levels in
the shelter immediately."
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