Steven Pinker, a psycholinguist at MIT and director of its Center for Cognitive Neuroscience, has a new book on how language works: "The Language Instinct: How the Mind Creates Language" (Morrow). He argues that language is not simply a cultural invention taught by parents and schools, but a biological system, --an instinct-- partly learned, and partly innate. To Pinker, a three year old toddler is a "grammatical genius", capable of obeying adult rites of language, similar to web-spinning in spiders or sonar in bats.