The “Pro‐drop” Parameter in Adult Second Language Acquisition

In this paper, it is proposed that adults learning second languages have particular problems when their mother tongue has activated a parameter of Universal Grammar which is not operative in the second language. It is suggested that the learner will carry the parameter over from L1 to L2, causing transfer errors. This proposal was tested on adult native speakers of Spanish learning English as a second language. Spanish, unlike English, is a “pro‐drop” language, having the following properties, all thought to be related by the “pro‐drop” parameter: (1) missing subjects, (2) free subject‐verb inversion, (3) that trace effects. Subjects were asked to make grammaticality judgments on a number of English sentences, including some with “pro‐drop” characteristics, which would have been grammatical in Spanish but were ungrammatical in English. It was found that Spanish speakers did accept many such sentences as grammatical, as compared to French‐speaking controls, who did not, and that Spanish speakers showed improvement with increasing levels of proficiency.