The Effect of Iconicity on Production in American Sign Language: An Electrophysiological Investigation

Iconicity refers to the structured mapping between a lexical form and the conceptual representation of what it means. In this dissertation, I present data from a set of three experiments using Event-Related Potentials (ERPs) that investigate the potential role of iconicity in sign production. In Study One, I present the findings from a picture-naming paradigm, which found the iconic signs were retrieved more quickly than non-iconic signs, particularly when there was a strong visual overlap between picture and sign. The production of iconic signs was additionally associated with increased N400 amplitude, indicating additional semantic processing, though this was reduced for the trials with the greatest visual overlap. In Study Two, I compared the effects of iconicity in a picture-naming task to that in an English-to-ASL translation task to explore whether the faciliatory effect of iconicity was general or task-specific. I found reduced response latencies and N400 amplitudes for iconic signs only in the picture-naming task, with no differences in the translation task, indicating that the effect of iconicity was task-specific. In Study Three, I extended the investigation of iconic signs in picture-naming paradigms by exploring the effects on two distinct manners of iconic mapping: perceptual vs. motoric iconicity. As in Study Two, reduced N400 amplitudes were observed compared to non-iconic signs, but there were no differences in response latencies. Through the use of Laplacian transformations, I compared the distribution of effects for perceptually-iconic signs, which map onto how the referent is perceived, and motorically-iconic signs, which map onto how the referent is handled. I found increased activation at frontal and central electrode sites for perceptually-iconic signs, and increased activation at parietal sites for motorically-iconic signs. These findings suggest that perceptually-iconic mappings engage the ventral stream, while motorically-iconic mappings engage the dorsal stream. Overall, this ...