The Language Instinct: How the Mind Creates Language

by Steven Pinker

To get English, one appends a single bit of information saying that the order within an X-bar is “head-first.” To get Japanese, that bit of information would say that the order is “head-last.” Similarly, the other super-rule (the one for phrases) can be distilled so that left-to-right order boils away, and an ordered phrase in a particular language can be reconstituted by adding back either “X-bar-first” or “X-bar-last.” The piece of information that makes one language different from another is called a parameter. In fact, the super-rule is beginning to look less like an exact blueprint for a particular phrase and more like a general guideline or principle for what phrases must look like. The principle is usable only after you combine it with a language’s particular setting for the order parameter. This general conception of grammar, first proposed by Chomsky, is called the “principles and parameters” theory.