The popular view that children have an advantage in learning a second language has considerable support in research, although it is not uncontested. One approach proposes that the child possesses a unique capacity for language that the adult no longer has. Another view argues that the child's brain is more flexible. A third approach assumes that language acquisition is innately determined and depends on some necessary neurological factors and unspecified minimum linguistic input during a critical period of brain lateralization of language specialization. Some recent research on the relationship of age differences and second language acquisition among children and between children and adults refutes the generalized early sensitivity hypotheses. Some of the age controversy also rests in methodological questions. In addition to physiological and age-related factors, the elements of motivation, attitude, and social-psychological distance are very important, the last being especially important in acquisition of phonology and eventual overall proficiency. Pragmatics and semantics may also provide some explanation for early sensitivity, including the idea that the communicative demands on adults are greater than they are for children. (MSE)