(1928–): a psycholinguist who proposed that human beings have an innate ability for language . Language acquisition is facilitated by the language acquisition device , or LAD, which operates on the speech that we hear as infants. Chomsky believed that the LAD was pre-programmed with the universal rules of grammar. By hearing speech in a specific language (such as English), the LAD is able to extract from its universal rules those which are appropriate for that language. Chomsky suggested that children quickly develop transformational rules which enable them to extract the same meaning (deep structure) from different word orders (surface structure). For example, in the sentences ‘The dog chased the boy’ and ‘The boy was chased by the dog’, the surface structures are different, but the deep structures are the same.