Since the cerebellum handles physical coordination, it makes sense that a young animal or human might spend a lot of time leaping, running, and chasing during the period that his cerebellum is forming new connections. The locomotor play period also coincides with the period when muscle fibers are turning into either fast-twitch or slow-twitch fibers. (Fast-twitch fibers give you the kind of short-lasting blasts of power you need for sprinting; slow-twitch fibers give you the long-lasting, endurance strength you need to run a marathon. Your heart would have to have slow-twitch fibers, or you’d be dead.)
So far this finding is only a correlation, and we don’t know from a correlation whether it’s the locomotor play that’s causing the cerebellar development, or the cerebellar development that’s causing the locomotor play, or both, or neither. Researchers will have to run controlled experiments to answer those questions. But my guess is play probably does help brain development. That makes me worry about all the computer games kids play today. I don’t know whether the overall amount of locomotor play American children do has gone down, but if it has that’s probably not good. When I was a child we didn’t have game systems or computers or cable TV; we had two recesses a day at school instead of just one; and the only time of the week when kids could watch cartoons was Saturday morning. To me it seems like we probably did more locomotor play if only because we didn’t have anything else to do. If locomotor play is important to developing the brain, I wonder whether children today are getting enough of it.
This is a bigger question than just whether or not kids grow up to be well-coordinated adults. Physical movement is probably the basis of a huge amount of academic, social, and emotional intelligence. A lot of major psychologists, including Jean Piaget, the Swiss psychologist who mapped out the stages of children’s cognitive development, have said that movement is basic to learning, and I agree. My drafting students who’ve never learned to draw physically, holding a pencil in their hand and moving it across a piece of paper, can’t draw at all on the computer. You have to learn to draw by hand first and then move to the computer. Virtual drawing isn’t a substitute for the real thing. I’ve seen this over and over again. Piaget said children learn by physically manipulating objects and seeing how they work. That’s movement. So if kids aren’t getting as much locomotor play now as they did in the past, that could be a problem not just for coordination but for learning.
Physical movement is probably what caused the brain to evolve in the first place, as a matter of fact. Dr. Rodolfo Llinas, a neuroscientist at NYU who wrote I of the Vortex: From Neurons to Self, says the brain evolved because creatures needed a brain to help them move around without knocking into things.29 He gives the sea squirt as the ultimate example of what having a brain is all about. The sea squirt is a primitive organism with about three hundred brain cells that starts out looking something like a tadpole, and ends up looking a little bit like a turnip. For the first day of its life it swims around until it finds a permanent spot to latch on to. Once it finds its spot, it doesn’t move again for the rest of its life.
Here’s the interesting part: while it is swimming it has a primitive nervous system, but once it becomes attached to an object it eats up its own brain. It also eats its own tail and tail muscles. Basically the sea squirt begins life as a kind of tadpole, with a tadpole-like brain, and then turns into an oyster-class creature. Since the sea squirt isn’t going to move ever again, it doesn’t need a brain.
Dr. Llinas’s theory is that we have brains so we can move. If we didn’t move we wouldn’t need brains and we wouldn’t have them. So I won’t be surprised if Dr. Byers and Dr. Walker are right that one of the primary purposes of play is to develop the brain.
ANIMAL ROUGHHOUSING
No one knows exactly why young animals and humans play with their friends and siblings, either. We do know social play always means roughhousing, which has led a lot of behaviorists to reason that play fighting must teach animals how to win a fight when they’re grown up. On the face of it that always sounded logical, because young males usually do more play fighting than young females, the same way adult males do more real fighting than adult females. Behaviorists figured the play fights were practice for the real thing.
But when researchers tried to establish a direct connection between roughhouse play and adult fighting in squirrel monkeys they didn’t find any connection. The squirrel monkeys who played the most didn’t win more fights as adults, and the monkeys who won the most play fights when they were young didn’t necessarily win the most real fights when they were grown up. There was no correlation one way or the other. That doesn’t disprove the hypothesis, but it doesn’t support it, either.
Another interesting fact: play fighting is nothing like real fighting. A lot of the moves that happen in real fighting never happen at all in play fighting, and the ones that do, happen in a different sequence.
We also know that the brain circuits for aggression are separate from the brain circuits for play. Testosterone, which can increase aggression, either has no effect on play fighting or actually reduces it. Sometimes roughhousing play will turn into a real fight, but inside the brain rough play and real aggression are two different things.
The other piece of evidence that play fighting isn’t about learning how to win is the fact that all animals both win and lose their play fights. No young animal ever wins all his play fights; if he did, nobody would play with him. When a juvenile animal is bigger, stronger, older, and more dominant than the younger animal he is play fighting with, the bigger animal will roll over on his back and lose on purpose a certain amount of the time. That’s called self-handicapping, and all animals do it, maybe because if they didn’t do it their smaller friends would stop playing with them. This is also called role reversal, because the winner and the loser reverse roles.
Role reversal is such a basic part of roughhouse play that animals do it when they play games like tug-of-war, too. A friend told me a story about her mixed-breed dog, when he was a year old and fully grown, playing with the four-month-old Labrador puppy next door. The new puppy was about a third his size, but Labradors are fearless and up for anything so she wasn’t fazed by his size. The two dogs liked to play tug-of-war with a rope toy my friend had out on his terrace, but of course my friend’s dog was so huge compared to the puppy that it was no contest. If he used all his strength he’d end up just whipping the puppy around the terrace like a Frisbee.
But that’s not what happened. Pretty soon my friend noticed that the puppy was “winning” some of the tugs. First my friend’s mutt would pull the puppy backward across the terrace, then the puppy would pull him backward a way. My friend said her dog was “keeping the puppy in the game,” and I’m sure she’s right.
Some behaviorists say that the fact that all animals self-handicap might mean that the purpose of play fighting isn’t to teach animals how to win but to teach them how to win and lose. All animals probably need to know both the dominant and the subordinate role, because no animal starts out on top, and no animal who lives to old age ends up on top, either. Even a male who is going to end up as the alpha starts out young and vulnerable. He has to know how to do proper subordinate behaviors.
PLAY AND SURPRISE
Marek Spinka, an animal researcher in the Czech Republic, has created a general hypothesis of play in animals. His theory is that play teaches a young animal how to handle novelty and surprise, such as the shock of being knocked off balance or a surprise attack.
If Dr. Spinka is right, that would explain why play fighting is so different from real fighting, because a play fight has to be constantly surprising to teach the young fighters to respond to novelty. Dr. Spinka’s theory also goes along with self-handicapping, since changing roles in the middle of a play fight means that the animals put themselves in roles they don’t normally have. A normally dominant young animal puts himself in the subordinate role, and a normally subordinate young animal puts himself in the dominant role. That’s a novel situat
ion.
Dr. Spinka’s theory is probably related to Dr. Llinas’s research on the brain and movement. Dr. Llinas says that a brain has to do three things to allow its owner to move: it has to set goals (where do I want to move to?), it has to make predictions (if I move this way will I crash into that tree?), and it has to rapidly process tons of incoming sensory data to make sure its predictions are coming true and its owner is getting where he wants to go in one piece.
All of that is a pretty good description of what happens in almost any kind of play in young animals, whether it’s locomotor or social or object play, which is playing with any kind of object, like a ball or a stick. One time I watched Red Dog playing with a plastic bag in the field next to Mark’s house. It was a windy day, and she would pick up the bag, carry it upwind to the fence, then put it down on the ground where the wind would catch it and blow it across the field to the other side. She’d chase the bag the whole way across the field and then, when she got to the fence, she’d catch the bag and bring it back to the upwind side where she could put it back down so the game could start all over again. It’s hard to see any reason for that game other than the fun of setting goals (I’m going to chase that bag across the field and catch it), making predictions (which way do I have to move to catch that bag?), and rapidly processing a lot of incoming sensory data from her race across the field. When you watch a young animal doing object play it really does look like they’ve got to be developing their basic brain functions in some way.
Social play has all of the same qualities. Mark likes to play a “go fishing” game with Red Dog where he takes a bullwhip and flips the tip out and lets Red Dog grab on to it. Then he says, “Oh, I’m going to reel in a big one!” That’s a social game, and it’s pure locomotion. When you look at what young animals do when they’re playing, and put that together with the fact that animals do the most physical play while the cerebellum is forming connections, I think we’ll probably find out that play is an important way that a young animal develops its brain’s ability to guide active movement.
CURIOUSLY AFRAID
So far, research is showing that the primal core emotions—rage, prey chase drive, fear, and curiosity/interest/anticipation—are handled by separate circuits in the brain. That doesn’t mean that more than one circuit can’t be turned on at the same time, or that one emotion can’t trigger another.
A friend of mine tells a story about her six-month-old mixed-breed dog’s reaction to her husband when he came home from a two-month research trip overseas. When the dog saw her husband he was overcome by terror and joy at the same time. He hit the floor in fear, crying and screaming, and at the same time he kept lifting his eyes up to the husband and frantically wagging his tail in greeting. Then he’d jerk his head back down and carry on screaming and cowering, all the while creeping along the floor on his belly toward the husband. My friend said it was exactly like the dog thought he was seeing a ghost. He was terrified and overjoyed in the same moment, seeing someone he thought he would never see again.
That’s a clear case of an animal having two warring emotions at the same time, and it stands out because you see this so rarely. In real life, animals seem to feel emotions one at a time, with one important exception: the emotions of fear and curiosity. ESB research shows that curiosity and fear come from different circuits in the brain, and you can turn each one on separately through electrical stimulation without automatically turning on the other. But I have observed that prey animals often feel both emotions at the same time. I don’t know whether predator animals also experience both fear and curiosity at the same time, but I expect they probably do.
I’ve already mentioned that cows will investigate scary new objects or people in their environment. If you stand still in their pasture they’ll start to walk up to you because they’re curious. But if you make even a tiny movement with your hand they’ll jump right back, because they’re also afraid. Then as soon as you stop moving, they’ll resume the approach. When they get about four feet away they’ll stretch their heads out as far as they can so they don’t have to get any closer than they absolutely have to, and then their tongues will come out another eight inches so they can give you a good licking and sniffing. They’re still scared, though, because any little rapid movement, like your hair or your jacket blowing in the wind, will frighten them off again.
This goes on for fifteen or twenty minutes tops, and then they get bored with you. I tell photographers, “You’ve got fifteen minutes to get your pictures.” After that the cattle won’t come up to you again, and they won’t let you come up to them. They’ll just move away if you try.
The way they act is so striking that I’ve had more than one person who didn’t know anything about cattle go out to a pasture with me and say, “She acts like she’s curiously afraid.” That is a perfect description of how cows react to novel stimuli: curiously afraid. It’s the only example of animals being ambivalent that I’m used to seeing as a matter of course.
BREEDING EMOTIONS
Apart from the ESB studies, another piece of important evidence that the core emotions each have their own separate circuits is the fact that you can use selective breeding to change one without changing the other. We know this from a quail study done in France by Jean-Michel Faure. Dr. Faure looked at two different genetically inherited emotions: fear and social reinstatement, which means the tendency for an animal to want to get up close to his buddies.30
They tested this by putting a group of quail in a cage at one end of a treadmill, and then putting one lone quail on the treadmill going in the opposite direction from the cage. The quail had to run against the moving treadmill belt to get back to the cage. They measured how hard the quail tried to get back to his friends.
They also measured each quail’s fear level and then correlated fear with social reinstatement. Their first set of findings was what they predicted: high fear and high social reinstatement go together. The more fearful the bird, the harder he tried to get back to his group. You see that in all kinds of animals, including predator animals who don’t need to stick together to be safe. Marmalade cats are high-fear for cats and they’re also high-social. No one knows why, but it’s true. They’re super-affectionate; they’ll eat up petting, much more so than other cats. But if you make a rapid movement a marmalade cat is the first to run away.
The next part of the experiment is really important. They used selective breeding to see if they could separate fear and social reinstatement—and they could do it easily. It was not hard at all to breed a high-fear quail who didn’t care about getting to his buddies, or a high-social quail who wasn’t afraid of anything. Even though in real life the two emotions go together, in the brain they’re separate.
We have some evidence for this in people, too. Various studies have shown that positive and negative emotions are probably created by different chemical systems in the brain. That’s not surprising, but what is surprising is the fact that positive and negative emotions aren’t inversely related. If you use a medication like Paxil or Prozac to lower negative emotions in a normal person, you don’t automatically raise his positive emotions. They’re separate systems.31 (This probably explains why people with bipolar disorder can have mixed states, when the person is excited and maybe even euphoric at the same time that he’s highly irritable.)
Intentionally or unintentionally, humans often separate animal emotions that normally go together through selective breeding programs. For instance, take the idea of breeding an animal for low fear. That might sound like a good idea, because high fear levels can make an animal nervous, high-strung, and hard to manage. But fear is an important emotion, and a person or an animal with abnormally low fear levels can be dangerous. He’s dangerous, because in nature fear rides herd on aggression. A dog with normal fear levels might want to get in a fight with a rival, but he’s also scared of getting hurt and that slows him down. The dog who’s fearless doesn’t think twice.
You see that in humans, too.
A fearful boy is a lot less likely to start fights than a fearless one. It’s not that the fearful boy doesn’t get mad; he does. Anger and fear are separate emotions, and a high-fear person or animal can feel as much anger as a low-fear person or animal. The difference is that fear keeps an angry person from going too far. There’s some interesting research on this in men and women, too. Males get in more physical fights than females, but females have just as much anger, and in some studies show more indirect aggression, like gossiping about a person they don’t like or excluding them from the group, than males. So far psychological research has found that the reason women have as much anger as men but don’t get in as many physical fights is that they also have higher levels of fear in angry situations. Fear is a constraint on physical aggression.
People take a big risk when they try to breed less fearful dogs. They could end up with some very dangerous animals. On the other hand, so far we’re getting away with it with Labrador retrievers. Labs are low-fear and low-aggression, which is something you don’t see in nature. I’m sure this is because breeders have been selecting for lower levels of both emotions. At least, I hope that’s what they’re selecting for. But with Labs, too, breeders are starting to see some of the problems that kick in from the traits that we don’t realize are genetically connected.
One of the problems comes from the fact that we’re breeding for calm/calm/calm, and we’re starting to get a Lab who’s so calm he’s abnormal. If you do something aggressive like grab him by both jowls he doesn’t react. People are also breeding the startle out of Labs, so if a car backfires he won’t jump and run off with the blind person he’s supposed to be leading. That makes Labradors good with children, who can be rough and unpredictable.
Labs have low pain, too, although that may be a trait they’ve always had, since as working dogs in Newfoundland they had to jump into icy water to get fish out of fishing nets. You can still see that behavior in Labs today. A young Labrador puppy will jump in a little kids’ wading pool and start pawing the water like crazy, like he’s trying to catch the fish in there.
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