Phonological activation in Hong Kong deaf readers: Evidence from eye movements and event-related potentials

Abstract

Understanding the roles of spoken and sign phonological code in reading processes is important for educators of deaf and hard-of-hearing students. However, the pool of data on this topic is limited and has mostly centered on readers of alphabetic languages. In places like Hong Kong, where deaf signers are relatively few, the shortage of research on phonological processing during reading is even more severe. This thesis addressed this problem by investigating the cognitive processes underlying Chinese reading in Hong Kong deaf readers using two methodological approaches, eye movements and event-related potentials, across four separate studies.

Studies 1 and 2 used the error disruption paradigm with eye-tracking to investigate the patterns of orthographic and phonological activation in hearing and deaf readers. The hearing reader data suggested that they rely mostly on orthography to access word meanings in early processing. However, early phonological activation was found to be facilitated top-down by semantics when targets were predictable. The deaf readers were also found to rely primarily on orthographic information to access word meanings, but phonological code played a role in late processing and was modulated by contextual predictability and reading level. Study 3 used a parafoveal preview paradigm with eye-tracking to investigate how sign phonologically related previews affect reading processes in Hong Kong deaf readers. The pattern of results suggested that these readers activate sign phonological representations when reading Chinese words and that different sign phonological parameters (i.e., handshape, location, and movement) have different effects on parafoveal processing.

Study 4 investigated orthographic, spoken phonological, and sign phonological processing in Hong Kong deaf readers using two error disruption paradigms with ERPs, focusing on the P200 and N400 components. The results for Experiment 1 revealed that N400 amplitudes were reduced in the orthographic condition, which suggested that orthographic representations were facilitating lexical access. In the homophonic condition, N400 amplitudes were increased in the right central eleci trodes. In Experiment 2, P200 amplitudes were significantly reduced in the left anterior electrodes in the sign phonological condition. In sum, the results of Experiment 1 and Experiment 2 suggest that the early P200 component is modulated by sign phonology, and the later N400 component is modulated by orthography and spoken phonology in Hong Kong deaf readers.

In sum, these studies suggest that while deaf readers tend to activate word meanings directly through orthography, they can also activate spoken phonological and sign phonological codes. Consistently across the eye movement and ERP studies, the effects of sign phonological activation emerged in early stages of processing, and the effects of spoken phonology emerged in later stages of processing. The different time courses of spoken and sign phonological activation may be an indication that deaf readers tend to use sign representations to activate word meanings and spoken phonological representations for later integrative processes. In conclusion, these findings can be taken to suggest that both types of phonological code are important for deaf readers.