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

124 HOW THE MIND WORKSputers, after all, were not designed as room heaters; they were 1 designedto process information in a way that is meaningful to human users.The psychologists David Sherry and Dan Schacter have pujshed thisline of reasoning farther. They note that the different engineeringdemands on a memory system are often at cross-purposes. Naturalselection, they argue, responded by giving organisms specialized memorysystems. Each has a computational structure optimized for thedemands of one of the tasks the mind of the animal must fulfill. Forexample, birds that cache seeds to retrieve in leaner times have evolveda capacious memory for the hiding places (ten thousand places, in thecase of the Clark's Nutcracker). Birds whose males sing to impress thefemales or to intimidate other males have evolved a capacious memoryfor songs (two hundred, in the case of the nightingale). The 1 memoryfor caches and the memory for songs are in different brain structuresand have different patterns of wiring. We humans place two very differentdemands on our memory system at the same time. We have toremember individual episodes of who did what to whom, when, where,and why, and that requires stamping each episode with a time, a date,and a serial number. But we also must extract generic knowledge abouthow people work and how the world works. Sherry and Schacter suggestthat nature gave us one memory system for each requirement: an"episodic" or autobiographical memory, and a "semantic" or genericknowledgememory, following a distinction first made by the psychologistEndel Tulving.The trick that multiplies human thoughts into truly astronomical numbersis not the slotting of concepts into three or four roles but a kind ofmental fecundity called recursion. A fixed set of units for each role is notenough. We humans can take an entire proposition and give it a role insome larger proposition. Then we can take the larger proposition andembed it in a still-larger one, creating a hierarchical tree structure ofpropositions inside propositions. Not only did the baby eat the slug, butthe father saw the baby eat the slug, and I wonder whether the fathersaw the baby eat the slug, and the father knows that I wonder whetherhe saw the baby eat the slug, and I can guess that the father knows that Iwonder whether he saw the baby eat the slug, and so on. Just as an abil-