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

Thinking Machines 113in a single neural network. In this section, I will present a more generalclass of evidence. Does the content of our common-sense thoughts (thekind of information we exchange in conversation) require a computationaldevice designed to implement a highly structured rhentalese, or can it behandled by generic neural-network stuff—what one wag has called connectoplasm?I will show you that our thoughts have a delicate logical structuringthat no simple network of homogeneous layers of units can handle.Why should you care? Because these demonstrations cast doubt onthe most influential theory of how the mind works that has ever beenproposed. By itself, a perceptron or a hidden-layer network is a high-techimplementation of an ancient doctrine: the association of ideas. TheBritish philosophers John Locke, David Hume, George Berkeley, DavidHartley, and John Stuart Mill proposed that thought is governed by twolaws. One is contiguity: ideas that are frequently experienced togetherget associated in the mind. Thereafter, when one is activated, the otheris activated too. The other law is resemblance: when two ideas are similar,whatever has been associated with the first idea is automaticallyassociated with the second. As Hume summed up the theory in 1748:Experience shows us a number of uniform effects, resulting from certainobjects. When a new object, endowed with similar sensible qualities, isproduced, we expect similar powers and forces, and look for a like effect.From a body of like color and consistence with bread we expect likenourishment and support.Association by contiguity and resemblance was also thought to be thescrivener that fills the famous blank slate, Locke's metaphor for theneonate mind. The doctrine, called associarionism. dominated Britishand American views of the mind for centuries, and to a large extent stilldoes. When the "ideas" were replaced by stimuli and responses, associationismbecame behaviorism. The blank slate and the two general-purposelaws of learning are also the psychological underpinnings of theStandard Social Science Model. We hear it in cliches about how ourupbringing leads us to "associate' food with love, wealth with happiness,height with power, and so on.Until recently, associationism was too vague to test. But neural-networkmodels, which are routinely simulated on computers, make theideas precise. The learning scheme, in which a teacher presents the networkwith an input and the correct output and the network strives toduplicate the pairing in the future, is a good model of the law of contigu-