response). When verbal stimuli are used, subjects typically show a higher evoked response in the left hemisphere, indicating greater processing activity (Wood, Goff, and Day, 1971). In EEG studies, verbal stimulation results in depressed alpha wave activity in the left hemisphere (the presence of alpha waves indicates a resting or meditative state) (Morgan, McDonald, and MacDonald, 1971).
The Development of Cerebral Dominance and Language Acquisition
Much of the controversy on the issue of the neurology of language acquisition is concerned with the development of cerebral dominance in childhood and its relation to language acquisition, both in first and second languages. The history of this issue begins with Lenneberg (1967), who hypothesized that the development of cerebral dominance was complete by around puberty ("firmly established"). According to Lenneberg, the infant brain is not firmly lateralized; in case of damage to the left hemisphere, or in case of removal of the left hemisphere ("hemispherectomy"), the right hemisphere is able to assume the language function. Lenneberg presented evidence that suggested that this ability of the language function to "transfer" hemispheres lasts until puberty, a conclusion that appeared to be consistent with reports of better recovery from acquired aphasia in children under age 10 or so. After puberty, the right hemisphere did not appear to be able to assume the language function in case of injury to or removal of the left hemisphere and Lenneberg hypothesized that this was due to the fact that lateralization of language to the left hemisphere was now complete. The presence of some of the language function in the right hemisphere in children also might be responsible for their superior recovery from aphasia.
Lenneberg (see also Scovel, 1969) also hypothesized that the end of the development of cerebral dominance coincided with the close of a "critical period" for language acquisition, noting that "foreign accents cannot be overcome easily after puberty" (p. 176) and that "automatic acquisition (of second languages) from mere exposure... seems to disappear after this age" (p. 176). Lenneberg therefore proposed a biological explanation for child-adult differences in language acquisition attainment, a very serious claim for those of us interested in