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

Thinking Machines 137workspace or bulletin board visible to all of the demons in the system. Ina separate part of the system lies a larger repository of information, along-term memory, that cannot be read by the demons until pieces of itare copied to the short-term memory. Many cognitive psychologists havepointed out that in these models the short-term memory (communal bulletinboard, global workspace) acts just like consciousness. When we areaware of a piece of information, many parts of the mind can act on it.We not only see a ruler in front of us but can describe it, reach for it,deduce that it can prop up a window, or count its markings. As thephilosopher Stephen Stich has put it, conscious information is inferentiallypromiscuous; it makes itself available to a large number of information-processingagents rather than committing itself to one alone. Newelland Simon have made headway in understanding human problem-solvingsimply by asking a person to think aloud when working on a puzzle.They have nicely simulated the mental activity using a production systemwhere the contents of the bulletin board correspond step for stepwith the person's report of what he is consciously thinking.The engineering specs of information access, and thus the selectionpressures that probably gave rise to it, are also becoming clearer. Thegeneral principle is that any information processor must be given limitedaccess to information because information has costs as well as benefits.One cost is space: the hardware to hold the information. The limitationis all too clear to microcomputer owners deciding whether to investin more RAM. Of course the brain, unlike a computer, comes with vastamounts of parallel hardware for storage. Sometimes theorists inferjiratthe brain can store all contingencies in advance and that thougjafcan bereduced to one-step pattern recognition. But the mathematics of a combinatorialexplosion bring to mind the old slogan oj^fTV: Too much isnever enough. Simple calculations show that^he number of humanlygraspable sentences, sentence meanings^^phess games, melodies, seeableobjects, and so on can exceed the nefmber of particles in the universe.For example, there are thirty to^flrty-five possible moves at each point ina chess game, each of wj*fcn can be followed by thirty to thirty-fiveresponses, defining about a thousand complete turns. A typical chessgame lasts fortvKfrns, yielding 10 120 different chess games. There areabout 10 70 Mtfficles in the visible universe. So no one can play chess bymemorising all the games and recognizing every sequence of moves. Thesamg'fs true for sentences, stories, melodies, and so on. Of course, somecombinations can be stored, but pretty soon either you run out of brain