Why did Luis Suarez sink his teeth into Giorgio Chiellini's shoulder? - Is he a victim of child-like impulsivity or could he be a vampire? Neither of these is the case, so let me review four possible reasons for his extraordinary behaviour.
1. The Internal Robot
Anyone who watched Suarez seize the moment to score when England's Steven Gerrard headed a long goal kick back towards his own goal, was amazed by the speed-of-light response of Suarez to an unpredicted - nay, unpredictable - event. Here was near-instantaneous judging of an unfamiliar situation and the execution of a brilliant, complex set of bodily responses to it. Here was a sort of genius at work.
To engage in this sort of cognition at lightning speed, you must rely on parts of the brain which function far too fast to be consciously monitored. This includes regions called the cerebellum and striatum, where highly complex mental operations can be partially automated and "run off" at high speed.
But to let these automatic systems - think of them as very smart internal robots if you like - do their work, you need to "switch off", or at least tone down, potentially interfering activity from the ponderously slow parts of the brain involved in conscious thinking and decision-making. To unleash his genius, in other words, Suarez has to enter a mental zone of relative mindlessness.
The upside of inhabiting this zone is that you can let the robots do their work. But the downside is that among them are one or two little devil-robots - negative habits which can only be let free when the conscious mind is turned down. And one of these - unfortunately for Suarez and Chiellini - is the troubling little habit of biting.
The expression of genius on the soccer field requires high levels of physiological arousal - a state of super-alertness involving racing heart, dilated pupils, rapid breathing and super fast reactions. This state is common to many different types of emotion - excitement, fear, challenge, anger and sex, for instance.
Suarez needs peak levels of arousal for his brain to perform its magic, but if arousal gets too high, it can tip the person over into muddled thinking and consequent strange behaviours. It is a bit like the "death zone" for airliners, which, at high altitudes, must keep their speed within very narrow limits if they are not to break up on one hand, or stall on the other.
Suarez's peak performance can tip into a state of confusion, where emotions are muddled up because of their common physiological underpinning. So, for instance, excitement or fear can easily be misinterpreted by the robot mind as anger - hence the biting.
So why can't he say to himself "Oh, I'd better not do this or else I will get a 9 match ban?" First, the part of his brain capable of thinking this only does so about half a second after his robot brain has activated the bite. Second, it is a bit like asking someone in the peak of sexual arousal to suddenly stop and consider whether their partner might have a sexual disease or not - once a person is in this state, then the slow-acting high level brain areas find it very hard to keep up with the fast-acting robot brains.
Millions of people across the world do things to themselves which hurt - for instance pulling out their hair or even cutting themselves. A common reason for these self-harming acts is that they release unpleasant tension. Even though the long-term consequences are bad - baldness, scarred arms or, dare I say, 9 match bans - the immediate effects are rewarding, a blessed relief from unbearable tension.
I have little doubt that Chiellini and his colleagues would have been niggling and harassing Suarez in and out of the box and that tension and frustration would have been building up in him. In his robot-mind state, the bite may well have given him that moment of relief - followed of course by dreaded realization of its consequences, but too late.
4. The Satisfaction of the Bite
What I am about to say here is speculative. But I wonder whether there is some primitive, visceral, perhaps almost sexual pleasure at sinking one's teeth into something or someone. Young children seem to gain enormous satisfaction in it, but learn to inhibit it. I wonder whether Suarez actually has satisfying revenge fantasies where he imagines himself sinking his teeth into someone who has offended or harmed him?
I imagine he has bitten quite a few people in his life, and it is probably a pretty effective deterrent against aggression in the sort of tough environments where he was brought up.
Should he be punished?
Of course he should. Some new little robot-routines involving fear of consequences have to be programmed into his cerebellum and that can't be done without punishment.
But the outrage against the bite is not particularly rational. Is a bite really worse than someone deliberately breaking another player's leg to finish his sporting career - as we have seen at least one famous, respected ex-player, now manager, do? The shock-horror should be confined to real sporting cruelty, not to theatricals which have no long-term effects.
Thursday's sentence of 9 international games is about right.