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Animals enjoy good laugh too, scientists
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,
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
"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
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
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
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."
Spanish excerpts, from Gabriel Romero:
La vida puede ser divertida, y no s�lo para los seres
Diversos estudios sugieren que los monos, los perros e
incluso las ratas r�en. La humanidad, por su parte, comenz� a re�r antes de
que pudiera hablar.
"De hecho, los circuitos neuronales que controlan la risa
existen en regiones muy primitivas del cerebro, y existieron formas de juego
y risa en otros animales antes de que los humanos pudieran hacerlo", se�al�
Jaak Panksepp, un neurocient�fico de la Universidad Estatal Bowling Green,
de acuerdo con la revista Journal Science.
Cuando los chimpanc�s juegan y se divierten con sus
semejantes, pueden producir gestos y sonidos similares a la risa humana, de
acuerdo con el texto de Pansepp difundido por la publicaci�n. Los perros
tienen una respuesta similar.
Cuando las ratas juegan tienen espasmos que se asemejan a
los que producen las carcajadas. Panskepp encontr� en un estudio previo que
cuando las ratas son cosquilleadas, r�en y se incoluvran socialmente con los
cient�ficos que desarrollaron tales pruebas.
Quedan a�n por realizarse m�s estudios sobre la risa
animal, y �stos podr�n explicar por qu� los humanos disfrutan de la risa.
Panskepp especula que, incluso, ello podr�a llevar al desarrollo de
tratamientos para la depresi�n.