Tickled Rats and Stand-up Comics

(Eric Lorentzen-Newberg/Flickr Open/Getty Images)

Play and laughter is found built in deep in the brain stem alongside rage and lust

Nature's Edge Notebook #18       

Observation, Analysis, Reflection, New Questions

Who would ever think of tickling a rat?

It's not the first thing that comes to mind when thinking about rats.

But back in the mid 1990s, Professor Jaak Panksepp, after years of work trying to discover where and how emotions reside in the brain, had a mischievous (and serious) idea early one morning.

But let him tell it.

Panksepp, whose voice on the phone has an audible twinkle even when explaining complicated science, went viral on YouTube with his demonstration - assisted by a couple of eager lab rats - that when he tickles them, they not only giggle and laugh - chirp, actually - they love it so much that they chase his tickling hand around their cage, begging for more.

Here's that brief You Tube video, followed by the professor's account of how his august scientific breakthrough - "Go tickle some rats!" - came to him in the first place:

As Panksepp describes there, the idea came to him because he had been observing "play behavior" in lab rats, during which he and his team slowly became aware that the rats at play were making soft little noises, so they rigged up the high-frequency microphones.

Imagine the professor's delight when his daring experiment (tickle rats) got such immediate results.

(One envious viewer of that YouTube clip even commented , "How can I get a job tickling laboratory animals for a living?")

An Ancestral Form of Laughter? An Enormously Robust Effect

We asked Panksepp via email whether this discovery was "an accident." His cheerful reply:

"It was pure intuition, perhaps coming out of an early morning dream… with the thought in my mind, after many years of work: 'Perhaps that sound is an ancestral form of laughter' … and I went to the lab that morning, and did the first experiment, tickling rats.

"Wow, what an enormously robust effect that was! - And after almost 20 years, we are still studying it."

Panksepp tells ABC News that it has even led to new findings about anti-depressant chemicals that may help humans, "since what we want in those sad folks is a somewhat happier brain" - like the brains of the tickled rats.

Panksepp adds that his team may even be gaining some new insights into the Attention Deficit Hyperactivity Disorder that seems to plague so many American elementary school students.

They have evidence that "abundant play can reduce ADHD-like symptoms in young rats."

And this is only a small part of Panksepp's research on the structural sources of emotion in the brain.

He and his colleagues have discovered seven emotional network systems deeply wired into the brain stems that we and other animals are born with.

He explained to us (on the phone from a scientific conference in San Francisco where he had just delivered a paper on play behavior) that these networks are built-in neural circuits, arising from our inborn DNA, that give rise to primal emotions.

And one of those primal emotion structures, they've shown, produces the urge, even the need, to play.

7 Hard-wired Emotional Brain Circuits, Including Play

Of the seven emotional circuits Panksepp and his team have found evidence for deep in the primal part of our brain, the first four are "positive," the remaining three "negative."  They are:

  1. The urge to seek, which links with and empowers the other six. This, he says, is the most ancient urge.
  2. The urge to lust - the desire needed for reproduction, continuation of the species.
  3. The urge to care - especially the caretaking of a parent, usually at first the caretaking of the mother, so that vulnerable young can survive … and then live long enough to reproduce their own offspring.
  4. The urge to play - (more below)
  5. The feeling of fear - spurring actions to escape danger.
  6. The emotion of rage - spurring actions that may protect oneself, family or group.
  7. The feeling of panic - different from fear in that it is more like the feeling an infant may have when cut off from its mother, so vital for survival.

Panksepp says play seems to be so deeply built in to our brain stems because in animals such as rats and humans (and many other species) survival depends so much on social attachments.

Play activity, he has found, helps stimulate and direct the brain to build neural pathways essential to basic social interaction.

The give-and-take of rough and tumble play, says Panksepp, the lessons such play inevitably delivers about not going too far and about being sensitive to others if the fun of play is to continue, "really allows animals (including humans) to learn about their social world."

He has done experiments showing that play behavior activates many of the genes in the "higher" parts of the brain - the outer brain, called the cortex, that does a lot of thinking about things and feelings, and conscious judging and deciding.

Panksepp says he believes the cortex of newborns is, in a sense, "empty" - that, at birth, it is waiting to be filled with impressions and lessons from the world it is born into - while the inner brain stem is already equiped to provide the various emotions that will impel and protect the newborn as those lessons are learned.

Play behavior is so ingrained, he says, that even when the cortex - this outer brain - of a rat has been completely removed surgically, leaving only the more ancient sub-cortical brain systems intact, the rat continues to display normal play activity.

Like Professional Wrestling, But With Chirping … and a Biological Right

We asked Panksepp what normal play looks like in rats.

"Like professional wrestling," he told us, "only there's a lot of chirping" - the giggling laughter picked up by his special microphones.

Panksepp even suggests that fulfilling the urge to play may be a sort of biological right, at least in humans.

Suppress the natural urge to play, or channel it too narrowly (which can amount to the same thing) and, he suggests, it may debilitate some of a child's neural networks:

"Considering that play helps program higher social circuits in our cognitive minds, it is essential for this right of every child to be adequately expressed, within our … cultural constraints," he says. "If we do not develop cultural landscapes where our children's most important urges can be channeled into productive pro-social activities, we will eventually have more childhood problems."

He says he has reason to suspect that such play suppression might even lead to  more ADHD and low level autism.

Rats Like to Listen to Other Rats Chirping.

(What Is Laughter For?)

And what are the rats' chirping giggles and laughter actually for?

Panksepp cautions that it can be hard to investigate, much less prove, exactly why evolution chooses specific behaviors, but he does offer these scientific observations:

"We know it (the chirping) signals positive affect (feelings, general mood), especially social affect … and we know the circuit-arousals are rewarding because animals self-stimulate every site (in the brain) where one gets those wonderful chirps," he writes in an email.

Panksepp adds this, which may even shed light on our natural attraction to groups of people who are laughing, and to some stand-up comedians:

"We also know that rats like to listen to other rats chirping, and to be with chirping rats, just like humans gravitate toward laughter, and like to be with happy people.

"Evolutionarily, I suspect," he says, "it facilitates social living and cooperative activities, just like our own laughter."


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This is the eighth in a series on animal intelligence and the science of play behavior:

1-   " Hunting With a Most Endangered Hunter - Dateline Botswana" At:    

                   http://abcn.ws/rI6Obx             (Nature's Edge Notebook #11)

2-  "Dogs Use Subway, Cat Takes Bus…" At:

                   http://abcn.ws/zXPpDd            (Nature's Edge Notebook #12)

3-  "Who Needs Words? Crows?  You? Wild Gorillas? Alison Krauss? …" At: 

                   http://abcn.ws/wM25PJ           (Nature's Edge Notebook #13)

4-   "How Would a Prairie Dog Describe You? Just Ask One!" At:

                    http://abcn.ws/yIZ9it                   (Nature's Edge Notebook #14)

5-  "Dolphins Reported Talking Whale in Their Sleep: Freud's 'Royal Road to the unconscious'  may have surfaced at a pool in France." At:

                     http://abcn.ws/yXpddT          (Nature's Edge Notebook #15)

6-  "Fun and Play Are Key to Survival for Bears, Dogs, Humans, Birds, and Maybe Even Ants." At:

                     http://abcn.ws/z4kS2G               (Nature's Edge Notebook #16)

7- " Is Universe Made to Make You Giggle? Play Seen in Humans, Fish, Atoms, and the Universe. A Self-Organizing Quirkiness" is suspected by experts in nature itself …   from ants to atoms to distant galaxies. " At:

http://abcn.ws/ApUElY           ( Nature's Edge Notebook #17)