the study of psychological aspects of language. Experiments investigating such topics as short-term and long-term memory, perceptual strategies, and speech perception based on linguistic models are part of this discipline. Most work in psycholinguistics has been done on the learning of language by children. Language is extremely complex, yet children learn it quickly and with ease; thus, the study of child language is important for psychologists interested in cognition and learning and for linguists concerned with the insights it can give about the structure of language. In the 1960s and early '70s much research in child language used the transformational-generative model proposed by the American linguist Noam Chomsky; the goal of that research has been to discover how children come to know the grammatical processes that underlie the speech they hear. The transformational model has also been adapted for another field of psycholinguistics, the processing and comprehension of speech; early experiments in this area suggested, for example, that passive sentences took longer to process than their active counterparts because an extra grammatical rule was necessary to produce the passive sentence. Many of the results of this work were controversial and inconclusive, and psycholinguistics has been turning increasingly to other functionally related and socially oriented models of language structure.