When IBM's Deep Blue supercomputer edged out world chess
champion Garry Kasparov during their celebrated match in 1997,
it did so by means of sheer brute force. The machine evaluated
some 200 million potential board moves a second, whereas its
flesh-and-blood opponent considered only three each second, at
most. But despite Deep Blue's victory, computers are no real
competition for the human brain in areas such as vision,
hearing, pattern recognition, and learning. Computers, for
instance, cannot match our ability to recognize a friend from a
distance merely by the way he walks. And when it comes to
operational efficiency, there is no contest at all. A typical
room-size supercomputer weighs roughly 1,000 times more,
occupies 10,000 times more space and consumes a millionfold more
power than does the cantaloupe-size lump of neural tissue that
makes up the brain. How does the brain--which transmits chemical
signals between neurons in a relatively sluggish thousandth of a
second--end up performing some tasks fast