Have you ever made what seemed like a cool-headed and clever decision, only to look back later and wonder what on earth you were thinking of? Do you consider yourself to be well-informed about current affairs, but find yourself amazed by unexpected shifts in human behavior; even, on occasion, by riots and revolutions? When some entirely likely personal or large-scale disaster strikes, do you find yourself asking how this could possibly have happened?

Welcome to being blindsided.

It seems that only human beings get blindsided. We don't seem to find gorillas tidying up after some disaster in the forest and muttering, ruefully, 'We really should have seen that one coming. What were we thinking of?' We humans, however, do this all of the time. There is an interesting and inescapable reason for this.

The human brain has evolved, not to enable us to think deep thoughts and to invent the internal combustion engine, but to keep us alive, to help us to find a mate and make babies and to enable us to live in large social groups, leveraging our individual powers to make us a formidable force in our environment. Large areas of the brain function entirely independently from what we experience as our conscious self.

If you reflect on your own behavior, you may come to agree that many of your most fundamental actions and reactions do not involve rational thought. We react before we are even aware of what we have done, driven by chemical messengers that operate within microseconds -- far quicker than the time necessary to pass messages 'up' to the conscious brain. We have come to describe these instinctive mental states as 'emotions.' which are highly efficient mechanisms for reacting to common situations: some of them are about escape and survival; others are about the incredibly sophisticated mechanisms that we have developed for understanding what other humans are thinking and feeling, and they enable us to deal with the very demanding challenges (in terms of brain power) of living in large social groups. We are brilliant at interpreting the nuances of gesture and facial expression that tell us whether a group member is well-disposed towards us or the reverse. We are rubbish, in general, at keeping a cool head when all the rest of our social group are buying the hot stock of the day or investing in houses that can supposedly only ever appreciate in value. We can't expect evolution to equip us to deal with highly complex issues that arose -- in evolutionary terms -- only yesterday. If early humans were helping themselves to a source of food, it would be a foolish group member who did not join in, and foolish group members tend not to survive to pass on their genes. When other members of our group today are helping themselves to some good thing, we are hard-wired to join in.

To be human is to be driven by ancient drives and instincts of which we are mostly or even completely unconscious. Our capacity for being blindsided stems from the fact that we have a truly impressive, rational, mind that lives alongside our more ancient, instinctive, emotional selves, and we have a self-image, carefully tended by our conscious minds, that won't allow us to believe we have just made a decision that was more appropriate a few millennia ago than it is today. The result is the unique experience of being human: we are so convinced of the power of our piercing intellects that we rationalise essentially instinctive decisions after the event: there is, we convince ourselves, a very good reason why we have bought that current hot stock or that second or larger house, bought in the middle of a housing boom; we persuade ourselves that the clever chaps at Enron or in Wall Street must know what they are doing, because they are helping us to make lots of money; we are certain that our society's carefully laid plans will ensure that we will be able to survive any possible disaster that might befall us; we assume that everyone shares our sense of community, and are deeply shocked when parts of that community take to the streets and start to loot and burn or to begin a revolution; because our brains are hardwired to be optimistic, we only worry about the threat of epidemics when there is a real and present danger - and we are still surprised and horrified when people actually start to die in large numbers.

There are two bits of good news. We can, as the ancient Greek philosophers proposed, attempt to know ourselves; to examine the motivations and mechanisms by which we reach our supposedly rational conclusions. A good trick is to start to practice on other people. Although a friend or colleague may say that they are doing something because of such and such a reason, it will be quite clear to you that their real motivation is altogether different: love (or lust) and self-interest are two common culprits. Now try the same procedure with your own behavior. The results are disturbing but illuminating.

On a truly positive note, we should embrace our complex, emotional humanity and exploit it to the full. We have created machines (computers) that are entirely 'rational'; they operate with impeccable logic, but they lack our human brilliance: the innovative ingenuity and instinctive empathy that enable us not only to devise astonishing potential solutions to the problems that we face but also to do devise socially feasible means of implementing these.

We may be blindsided, time and again, but we are not stupid.