Tickling Rats

At the stage reached by the age of three, and after ages four, five and six, play will be necessary. These are games which nature herself suggests at that age; children readily invent these for themselves when  left in one another’s company.

Plato, The Laws VII, 794

When you tickle a rat, it makes 50-kHz ultrasonic sounds or “chirps”. We know this because scientist Jaak Panksepp has tickled a lot of rats. Panksepp is a neurobiologist who, with psychotherapist Lucy Biven, wrote my holiday reading, The Archaeology of Mind. Panksepp doesn’t just tickle rats for fun. He is engaged in serious research. He noticed that rats make the same 50-kHz noise when they play among themselves, especially when that play is characterised by “pins” (think wrestling-style pins) and dorsal contact – the rough-and-tumble play that Panskepp is careful not to call play-fighting. (He is concerned that people misinterpret play as a form of aggression, and that parents may be causing developmental harm when they discourage the more boisterous forms of rough -and-tumble play.) That said, even rats’ rough-and-tumble play can sometimes turn into fighting. When rats actually fight, they make a lower 22-kHz ultrasonic sound and “when this happens, playful signs-the frantic hopping, darting and pouncing – immediately stop.”

So, after two years of observation (and tickling) the team proved that the 50-kHz ultrasonic chirps are rat laughter, and the 22-kHz sounds are “complaints.” His thesis is that all mammals share seven instinctive emotions, even if different species’ higher brain  functions can be very different. He labels the seven core emotions thus:

• SEEKING
• RAGE
• FEAR
• LUST
• CARE
• PANIC/GRIEF and
• PLAY

“It is hard to define play,” he says “but you know it when you see it. Perhaps the best general definition has recently (2005) been suggested by Gordon Burghardt, consisting of five criteria:

1. The adaptive functions of play are not fully evident at the time play occurs;
2. play is a spontaneous activity, done for its own sake, because it is fun (pleasurable);
3. play is an exaggerated and incomplete form of adult activities;
4. play exhibits many repetitive activities, done with abundant variations, unlike serious behaviors that are not as flexible; and
5. animals must be well fed, comfortable, and healthy for play or occur, and all stressors reduce play.”

Panksepp illustrates this last point with a personal anecdote “if a laboratory researcher has a pet cat at home and he is not careful to change his clothes before going to work, we will have a difficult time studying the play of rats because the odor of cats intrinsically scares rats, and fearful rats simply do not play.”

But why do we and other mammals share this instinctive play emotion? Well, as he says in his TED talk (below) science doesn’t answer the question why, it only answers “how.” But he does have some ideas about how play helps “the young to learn nonsocial physical skills like hunting, foraging and so on. It is also surely important for acquiring many social capacities, especially nascent aggressive, courting, sexual and in some species competitive and perhaps even parenting skills. It may be an essential force for the construction of the many higher functions of our social brains. Playful activities may help young animals learn to identify individuals with whom they can develop cooperative relationships and know who to avoid […] In short, the brain’s PLAY networks may help stitch individuals into the stratified social fabric that will be the staging ground for their lives.”

Though he doesn’t spend much ink on the higher brain function aspects of adult, human, play (games, sports etc) he does draw a comparison between the rough-and-tumble play he studies and the teasing repartee or word-play that can be observed in older humans.

All in all its been a very satisfying read, and I want to read more, especially his chapter on learning and memory. But for this post I’ll leave you with his TED talk which is an effective summary his 50 year career, and benefits it may be producing in the treatment of depression.