Abstract
The sensitive period as a developmental concept is discussed. Observations are made on various problems involved in attempting to explain adult difficulties with second language acquisition by invoking motivational and input factors. Sixty male Italian immigrants listened to English sentences masked with white noise at four signal-to-noise ratios. Comprehension scores were correlated with age of beginning English but were not predicted by number of years in the United States or by other variables investigated. Scores of those who arrived before early adolescence resembled those of native speakers, while those subjects who began English toward the end of adolescence showed a marked comprehension deficit. These results support the hypothesis that a sensitive period exists for the acquisition of a second language.