31.07.2015 Views

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

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

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

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

Thinking Machines 137workspace or bulletin board visible to all of <strong>the</strong> demons in <strong>the</strong> system. Ina separate part of <strong>the</strong> system lies a larger repository of information, along-term memory, that cannot be read by <strong>the</strong> demons until pieces of itare copied to <strong>the</strong> short-term memory. Many cognitive psychologists havepointed out that in <strong>the</strong>se models <strong>the</strong> short-term memory (communal bulletinboard, global workspace) acts just like consciousness. When we areaware of a piece of information, many parts of <strong>the</strong> 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 <strong>the</strong>philosopher Stephen Stich has put it, conscious information is inferentiallypromiscuous; it makes itself available to a large number of information-processingagents ra<strong>the</strong>r 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 <strong>the</strong> mental activity using a production systemwhere <strong>the</strong> contents of <strong>the</strong> bulletin board correspond step for stepwith <strong>the</strong> person's report of what he is consciously thinking.The engineering specs of information access, and thus <strong>the</strong> 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: <strong>the</strong> hardware to hold <strong>the</strong> information. The limitationis all too clear to microcomputer owners deciding whe<strong>the</strong>r to investin more RAM. Of course <strong>the</strong> brain, unlike a computer, comes with vastamounts of parallel hardware for storage. Sometimes <strong>the</strong>orists inferjirat<strong>the</strong> brain can store all contingencies in advance and that thougjafcan bereduced to one-step pattern recognition. But <strong>the</strong> ma<strong>the</strong>matics of a combinatorialexplosion bring to mind <strong>the</strong> 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 <strong>the</strong> nefmber of particles in <strong>the</strong> universe.For example, <strong>the</strong>re 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 <strong>the</strong> visible universe. So no one can play chess bymemorising all <strong>the</strong> 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 ei<strong>the</strong>r you run out of brain

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!