Learnability constraints on deaf learners' acquisition of English wh-questions.

This article explores deaf college students' knowledge of English wh-question formation in the context of government-binding theory and an associated learnability theory. The parameters of universal grammar (UG) that are relevant to wh-question formation are identified, and predictions are made regarding the learning of the English values of these parameters in accordance with the subset principle, which, it has been proposed, guides the acquisition of UG parameter values that define languages ordered as proper subsets. The results of two learnability tasks revealed that, despite years of exposure to English language input, many deaf learners have not internalized the positive evidence required to set the marked values of the wh-question parameters. This finding provides strong empirical support for the subset principle. Theoretical and educational implications are discussed.