We finally got a handle on the nature of psychological pain, which is very important for depression and other psychiatric disorders.  And then we said well there must be something fundamental about the social principal that is in the arena of joy.  What would it be?  And the answer was obvious that it must be playfulness.

Well my background is a great desire to understand the very foundations of mental life and the nature of consciousness and my perspective is that the lowest level of consciousness is affective experience, various feelings of goodness and badness.  Then we wanted to make a science of this and we couldn’t imagine making a science out of it without having solid animal models so we accept the obvious that animals have emotional feelings and we can finally understand the brain mechanisms and we decided to pursue emotions in the brain that no one else had ever touched.  And one of them was social bonding, social attachment, separation distress where animals feel psychological pain when they’re isolated from others and the reunion and the positive feelings which are mediated by opioids, oxytocin and prolactin, a variety of chemistry’s lead to a social bond.  So we finally got a handle on the nature of psychological pain, which is very important for depression and other psychiatric disorders.  And then we said well there must be something fundamental about the social principal that is in the arena of joy.  What would it be?  And the answer was obvious that it must be playfulness.  And there was not yet a science to play.  A lot of people had described play but no one had tried to analyze it in a really scientific experimental way.  So we decided to go with a good ole laboratory rat and we said well how do you get them to play in front of you?  The answer seemed pretty obvious.  You make them hungry for play by putting them alone for awhile and low and behold if you put the young ones together they played like the dickens, immediately, very robustly.  And we described the behavior in detail and we wanted to rapidly get into the brain and work out the brain mechanisms.  So along with a serious and enthusiastic students we initially analyzed just the physical dynamics of play and then eventually had a post doc Brain Knutson who said is their play sound and I said well nothing that we can hear with our ears.  He was a little perhaps despondent but I said not to worry because we have to listen to a very high register and if you’re interested we’ll get the equipment and you can listen in and see if there is play sounds.  He discovered there’s play sound immediately, the first day.  So he was a young scholar who had no experience in animal research and he made a discovery right away.  We studied that at the play vocalization and a possible indication of excitement about life in general, anticipating all the good things in the world and Brian went in that direction and it was very productive but I thought it was fundamentally a social response.  So when Brian departed I had an under graduate assistant who just interviewed Jeff Burgdorf and he took over and forced me to be much more in the lab again, showing him the ins and outs of doing research.  After many months of kind of just doing play vocalization a thought crossed my mind that maybe it was laughter and that very morning when I had the thought it came out of a dream, it came out of some primitive unconsciousness, I came into the laboratory and Jeff was waiting for me and I said Jeff, left’s go tickle some rats.  And he kind of looked at me with a moment of perplexity and said okay.  So we went and we tickled the first rat.