  The third reason for rejecting behaviorism is connected with Noam Chomsky. Chomsky has been one of behaviorism’s most successful and damaging critics. In a review of Skinner’s book on verbal behavior (see above), Chomsky (1959) charged that behaviorist models of language learning cannot explain various facts about language acquisition, such as the rapid acquisition of language by young children, which is sometimes referred to as the phenomenon of “lexical explosion.” A child’s linguistic abilities appear to be radically underdetermined by the evidence of verbal behavior offered to the child in the short period in which he or she expresses those abilities. By the age of four or five (normal) children have an almost limitless capacity to understand and produce sentences which they have never heard before. Chomsky also argued that it seems plainly untrue that language learning depends on the application of detailed reinforcement.  A child does not, as an English speaker in the presence of a house, utter “house” repeatedly in the presence of reinforcing elders.  Language as such seems to be learned without, in a sense, being explicitly taught or taught in detail, and behaviorism doesn’t offer an account of how this could be so. Chomsky’s own speculations about the psychological realities underlying language development include the hypothesis that the rules or principles underlying linguistic behavior are abstract (applying to all human languages) and innate (part of our native psychological endowment as human beings).  When put to the test of uttering a grammatical sentence, a person, for Chomsky, has a virtually infinite number of possible responses available, and the only way in which to understand this virtually infinite generative capacity is to suppose that a person possesses a powerful and abstract innate grammar (underlying whatever competence he or she may have in one or more particular natural languages).