One goal of our pyscholinguistic research is to examine what aspects of language processing and production may be universal and what aspects are affected by the particular characteristics of audition vs. vision or by the specific constraints on gestural vs. vocal articulation. Our laboratory has adapted and developed several psycholinguistic paradigms which permit exploration of real-time processing of a visual-spatial language. Our results indicate that lexical access and word recognition processes are similar for signed and spoken languages, but language modality effects are observed in the speed of sign identification. Our studies also show that signed and spoken languages use the same processing, mechanisms in resolving and interpreting pronouns, even though ASL uses spatial locations to convey co-reference. Finally, our language production studies indicate that signers exhibit "tip-of-the-fingers" effects, slips of the hand, and produce gestures in conjunction with signing. Our results primarily reveal similarities between the mechanisms involved in comprehending and producing both spoken and signed languages.
We are also conducting some of the first experiments using head-mounted eye tracking technology to study eye behaviors during the perception and production of ASL. We are investigating how the social and conversational functions of eye gaze interact with the requirements of eye gaze for sign perception. Another set of studies investigates eye movements during sign production. These studies address theoretical claims regarding the grammatical functions of eye gaze in ASL and identify how signers co-ordinate their eye movements with the linguistic structure of signed sentences. In addition, we are comparing the eye behaviors of native deaf signers with adult late learners (hearing and deaf) during sign perception and while signing. The use of eye gaze to mark linguistic structure is unique to signed languages, and the results of these studies provide insight into how language modality affects the nature of grammatical encoding and what eye gaze behaviors must be learned in order to perceive and produce ASL efficiently and effectively.