Verbal history

Chomsky's review of Skinner’s Verbal Behavior has been hailed as the most influential document in the history of psychology. This is especially true in my line of work.

In his book Verbal Behavior, psychologist B. F. Skinner wrote that language development occurs when: “..differential reinforcement shapes relatively unpatterned vocalizations into grammatically correct forms”. Linguist Noam Chomsky refuted this claim, declaring that principles of ‘differential reinforcement’ cannot ‘shape’ comprehension and construction of sentences never heard before. He goes on to say that behavioral psychology cannot possibly account for the way children learn languages. He argues that children do not acquire a finite set of well-formed sentences, but rather a system of rules from which they can generate an infinite set of well-formed sentences. Chomsky was so persuasive that psychologists adopted his linguistic principles as a method for observing language development. Chomsky’s ‘transformational grammar’ is a system of abstract rules designed to produce sentences of varying complexity starting from a simple conceptual-base. Sentences can be ranked in order of ‘derivational complexity’. Derivational complexity refers to the number of transformation rules required to produce complex forms from simpler forms. For example, a passive rule transforms a simple declarative sentence like “John hit the ball” into “The ball was hit by John”. A possessive rule transforms it into “My ball was hit by John”, adding another degree of complexity, and so on. Chomsky was right. Transcripts of early speech show a definite trend. Development does, in fact, occur in stages that correspond to levels of derivational complexity.

Presented at a seminar in language learning