Four eye movement experiments investigated whether readers use parafoveal input to gain information about the phonological or orthographic forms of consonants, vowels, and tones in word recognition when reading Thai silently. Target words were presented in sentences preceded by parafoveal previews in which consonant, vowel, or tone information was manipulated. Previews of homophonous consonants (Experiment 1) and concordant vowels (Experiment 2) did not substantially facilitate processing of the target word, whereas the identical previews did. Hence, orthography appears to be playing the prominent role in early word recognition for consonants and vowels. Incorrect tone marker previews (Experiment 3) substantially retarded the subsequent processing of the target word, indicating that lexical tone plays an important role in early word recognition. Vowels in VOP (Experiment 4) did not facilitate processing, which points to vowel position being a significant factor. Primarily, orthographic codes of consonants and vowels (HOP) in conjunction with tone information are assembled from parafoveal input and used for early lexical access.
Winskel, H 2011, 'Orthographic and phonological parafoveal processing of consonants, vowels, and tones when reading Thai', Applied Psycholinguistics, vol. 32, no. 4, pp. 739-759.