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

102 HOW THE MIND WORKSvegetable but that garlic is only a so-so example. And if we are td believethe Reagan administration when it justified its parsimonious schoollunch program, even ketchup is a kind of vegetable—though after afirestorm of criticism the administration conceded that it is not a verygood example of one. Conceptually speaking, we eschew the idea thatsomething either is or is not a vegetable and say that things can be betteror worse examples of a vegetable. Mechanically speaking, we no longerinsist that a unit representing vegetablehood be either on or off, butallow it to have a value ranging from 0 (for a rock) through 0.1 (forketchup) through .4 (for garlic) to 1.0 (for celery).We can also scrap the arbitrary code that relates each concept to ameaningless string of bits. Each bit can earn its keep by representingsomething. One bit might represent greenness, another leafiness,another crunchiness, and so on. Each of these vegetable-property unitscould be connected with a small weight to the vegetable unit itself.Other units, representing features that vegetables lack, such as "magnetic"or "mobile," could be connected with negative weights. Conceptuallyspeaking, the more vegetable properties something has, the better anexample it is of a vegetable. Mechanically speaking, the more vegetablepropertyunits are turned on, the higher the activation level of the vegetableunit.Once a network is allowed to be squishy, it can represent degrees ofevidence and probabilities of events and can make statistical decisions.Suppose each unit in a network represents a piece of evidence implicatingthe butler (fingerprints on the knife, love letters to the victim's wife,and so on). Suppose the top node represents the conclusion that the butlerdid it. Conceptually speaking, the more clues there are that the butlermight have done it, the higher our estimate would be that the butler did