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

120 | HOW THE MIND WORKSjust a very big collection of separate units; the units could just as easilyhave represented an inventory of isolated factoids that had nothing dowith one another. When nature presents us with objects that perfectlyfill a rectangular bank of pigeonholes, it's telling us that the objects mustbe built out of smaller components which correspond to the rows andthe columns. That's how the periodic table of the elements led to anunderstanding of the structure of the atom. For similar reasons we canconclude that the warp and weft of our thinkable thoughts are the conceptscomposing them. Thoughts are assembled out of concepts; theyare not stored whole.Compositionality is surprisingly tricky for connectoplasm. All theobvious tricks turn out to be inadequate halfway measures. Suppose wededicate each unit to a combination of one concept and one role. Perhapsone unit would stand for baby-eats and another for slug-is-eaten, orperhaps one unit would stand for baby-does-something and another forslug-has-something-done-to-it. This cuts down the number of combinationsconsiderably—but at the cost of reintroducing befuddlement aboutwho did what to whom. The thought "The baby ate the chicken whenthe poodle ate the slug" would be indistinguishable from the thought"The baby ate the slug when the poodle ate the chicken." The problem isthat a unit for baby-eats does not say what it ate, and a unit for slug-iseatendoes not say who ate it.A step in the right direction is to build into the hardware a distinctionbetween the concepts (baby, slug, and so on) and the rolesthey play (actor, acted upon, and so on). Suppose we set up separatepools of units, one for the role of actor, one for the action, one forthe role of acted upon. To represent a proposition, each pool of unitsis filled with the pattern for the concept currently playing the role,shunted in from a separate memory store for concepts. If we connectedevery node to every other node, we would have an auto-associatorfor propositions, and it could achieve a modicum of facilitywith combinatorial thoughts. We could store "baby ate slug," andthen when any two of the components were presented as a question(say, "baby" and "slug," representing the question "What is the relationshipbetween the baby and the slug?"), the network would completethe pattern by turning on the units for the third component (inthis case, "ate").