UC San Diego

This dissertation investigated the grammatical use of eye gaze in American Sign Language (ASL) in three experiments, all of which make use of head-mounted eye-tracking technology. Experiment 1 investigates the use of eye gaze to mark verb agreement by native signers of ASL. The results support the use of eye gaze as a verb agreement marker. However, the findings differ from previous claims that eye gaze marks object agreement across all three ASL verb types (agreeing, spatial, and plain). Instead, the data argue for a system of eye gaze agreement that marks verbs according to a universal accessibility hierarchy: Subject < Direct Object < Indirect Object < Locative. Experiment 2 investigates the acquisition of eye gaze agreement by hearing late learners of ASL. The focus is how language-specific properties, including modality, might influence the acquisition of a signed second language (L2). Beginning signers (> 2 years of sign exposure) do not direct their gaze appropriately when producing ASL verbs, indicating that the linguistic use of eye gaze does not occur "naturally," but must be learned. Proficient late-learners of ASL followed the eye gaze patterns we had observed for native signers, thus replicating our previous results. However, they overgeneralized the use of eye gaze, marking agreement for plain verbs as well as spatial and agreeing verbs. Overall, L2 learners of ASL eye gaze exhibit the same patterns of L2 acquisition found in spoken languages suggesting that modality had little if any affect on acquisition. Experiment 3 investigated whether directed eye gaze also occurs during the production of pronouns. The use of directed eye gaze to mark pronominal referents is predicted by some analyses of ASL pronominals. However, the results show no systematic gaze distinction occurring with pronouns, thus indicating that the underlying mechanism for verb agreement and pronominal reference is not the same. In sum, this research shows that an exotic language feature such as eye gaze can function as a syntactic marker that follows linguistic principles and can be learned