Steven Pinker -- How the Mind Works - Hampshire High Italian ...

138 HOW THE MIND WORKSor you start to superimpose the patterns and get useless chimeras andblends. Rather than storing googols of inputs and their outputs or questionsand their answers, an information processor needs rules:or algorithmsthat operate on a subset of information at a time and calculate ananswer just when it is needed.A second cost of information is time. Just as one couldn't store all thechess games in a brain less than the size of the universe, one can't mentallyplay out all the chess games in a lifetime less than the age of theuniverse (10 18 seconds). Solving a problem in a hundred years is, practicallyspeaking, the same as not solving it at all. In fact, the requirementson an intelligent agent are even more stringent. Life is a series t»f deadlines.Perception and behavior take place in real time, such as in huntingan animal or keeping up one's end of a conversation. And since computationitself takes time, information processing can be part of the problemrather than part of the solution. Think about a hiker planning the quickestroute back to camp before it gets dark and taking twenty minutes toplot out a path that saves her ten minutes.A third cost is resources. Information processing requires energy.That is obvious to anyone who has stretched out the battery life of a laptopcomputer by slowing down the processor and restricting its access toinformation on the disk. Thinking, too, is expensive. The technique offunctional imaging of brain activity (PET and MRI) depends on the factthat working brain tissue calls more blood its way and consumes moreglucose.Any intelligent agent incarnated in matter, working in real time, andsubject to the laws of thermodynamics must be restricted in its access toinformation. Only information relevant to the problem at hand should beallowed in. That does not mean that the agent should wear blinkers orbecome an amnesiac. Information that is irrelevant at one time for onepurpose might be relevant at another time for another purpose. So informationmust be routed. Information that is always irrelevant to a kind ofcomputation should be permanently sealed off from it. Information thatis sometimes relevant and sometimes irrelevant should be accessible to acomputation when it is relevant, insofar as that can be predicted inadvance. This design specification explains why access-consciousnessexists in the human mind and also allows us to understand some of itsdetails.Access-consciousness has four obvious features. First, we areaware, to varying degrees, of a rich field of sensation: the colors and