The brain is not a linear processing machine taking a bit of input and systematically processing it. Rather we are endowed with a brain that pattern matches.
Dr. Ralph Greenspan says(1):
In no sense does the brain work like a computer. Computers record, and computers have things stored in specific places that are stable. Our brains do none of that. When the great chess master Gary Kasparov lost to Big Blue everybody said “Aha, this machine can think!” Big Blue was not thinking. Big Blue was simply replaying the entire history of chess. That's not the way that Gary Kasparov or any human being plays chess. We do pattern recognition. Even though we are capable of logic, our brain does not operate by the principles of logic. It operates by selection of pattern recognition. It's a dynamic network. It's not an “if-then” logic machine.
When computers play chess they are effectively looking at all the moves available and working out (n) levels deep. While computers have surpassed us in the ability to play chess, largely through sheer brute force, there is an important point that's worth noting. For a while we kept up and even outplayed them, despite their dominance in processing power.
Think about it. Computers could do millions, even billions of computations per second. Their computational power was awesome. And for a time it meant nothing.
An excerpt from an awesome article by Nobel Laureate Herbert Simon offers some insight (2):
We have seen that a major component of expertise is the ability to recognize a very large number of specific relevant cues when they are present in any situation, and then to retrieve from memory information about what to do when those particular cues are noticed.
Because of this knowledge and recognition capability, experts can respond to new situations very rapidly- and usually with considerable accuracy. Of course, on further thought, the initial reaction may not be the correct one, but it is correct in a substantial number of cases and is rarely irrelevant. Chess grandmasters, looking at the chessboard, will generally form a hypothesis about the best move within five seconds, and in four out of five cases, this initial hypothesis will be the move they ultimately prefer. Moreover, it can be shown that this ability accounts for a very large proportion of their chess skill. For, if required to play very rapidly, the grandmaster may not maintain a grandmaster level of play but will almost always maintain a master level, even though in rapid play there is time for almost nothing but to react to the first cues that are noticed on the board.
We usually use the word “intuition” – sometimes also “judgment” or even “creativity” – to refer to this ability of experts to respond to situations in their domains of expertise almost instantaneously and relatively accurately. The streetwise slum resident has good intuition about how to react to the situations that are often encountered in a slum environment. The manager has good intuition about how to react to the situations that are often encountered in organizations. Both skills have the same basis in knowledge and recognition capability.
This is why we use a two step process for making effective decisions.
If you're interested in learning more about Herbert Simon—and you should be— I recommend reading Models of My Life.
(1) Seeking Wisdom
(2) How Managers Express their Creativity, Autumn 1986, The McKinsey Quarterly