Structural linguistics showed that the infinite variety of sounds in language was based on a few categories of contrast. Modern transformational linguistics extended this idea of phonetic structure to grammar. The work of motherhood, after all, converts an infant, whose needs are overwhelmingly governed by its "natural," biological impulses, into a mature cultural being for whom sentiment, symbol, and language are defining attributes. People eat certain kinds of foods on certain occasions not because they are good to eat, or because they supply a requisite amount of nutrients, but because they "are good to think with." At various times, cognitive anthropologists have collected the words used in native languages for kinship terms, plants, animals, colors, parts of the body, and diseases; in essence, virtually anything for which people have a working vocabulary. For cognitive anthropologists, the analytical implications of this strategy reflect their idealist assumptions about culture.