This article reviews the second language research on age-related differences, as well as first language work needed to disambiguate some of the findings. Five conclusions are drawn, (a) Both the initial rate of acquisition and the ultimate level of attainment depend in part on the age at which learning begins. (b) There are sensitive periods governing language development, first or second, during which the acquisition of different linguistic abilities is successful and after which it is irregular and incomplete. (c) The age-related loss in ability is cumulative (not a catastrophic one-time event), affecting first one linguistic domain and then another, and is not limited to phonology, (d) The deterioration in some individuals begins as early as age 6—not at puberty as is often claimed. (e) Affective, input, and current cognitive explanations for the reduced ability are inadequate. The capacity for language development is maturationally constrained, and its decline probably reflects a progressive loss of neural plasticity, itself possibly associated with increasing myelination.

This study explores the question of whether or not learners can consciously attend to both form and meaning when processing input. An experimental procedure is presented in which three levels of learners in four groups were asked to process information under four different conditions: attention to meaning alone; simultaneous attention to meaning and an important lexical item; simultaneous attention to meaning and a grammatical functor; and simultaneous attention to meaning and a verb form. Results suggest that learners, in particular early stage learners, have great difficulty in attending to both form and content. These results raise important questions for current discussions of the role of consciousness in input processing.

Speech rate (articulation rate and pauses) was examined for its relation to communicative success. Native English speakers (NSs) were paired with other NSs and with non-native speakers (NNSs). The subjects viewed a short film, the content of which they were to relay to their two partners independently. Communicative success was measured through comprehension questions addressed to the listeners at the completion of the task. Analyses indicated that although a slight majority of NSs slowed their speech rate for NNSs, they did not adjust articulation rate, but did significantly increase pause time. Neither speech rate nor articulation rate varied over the course of the narrations. Contrary to intuition, the subjects who successfully communicated the story to NNSs did not adjust their speech rate, while those who had difficulty communicating with NNSs increased pause time significantly. The implications of the findings are discussed, and suggestions for further research are made.

Studies of first and second language acquisition have indicated that when verbal morphemes first appear, they tend to mark aspectual distinctions in non-native-like ways. This study tested the hypothesis that in L2 acquisition, verbal morphemes initially mark lexical aspect—the temporal features inherent in the semantics of a predicate, independent of the time line—regardless of their function in the target language. To reduce the subjectivity that has weakened previous studies, operational tests—which entailed inserting a base-form verb phrase into a frame and then judging whether the result is acceptable—were used to determine lexical aspect for each of over 550 verb tokens in the corpus, based on an interlanguage sample from a native speaker of Spanish. The results of a chi-square test allow rejection of the null hypothesis—that lexical aspect and morphology are independent—at the .001 confidence level. Past marking was found to correlate with punctual aspect, -ing with durative.