Dyslexics exhibit an orthographic, not a phonological deficit in lexical decision

ABSTRACT

Dyslexia is theorised to be caused by phonological deficits, visuo-attentional deficits, or some combination of the two. The present study contrasted phonological and visuo-attentional theories of dyslexia using a lexical decision task administered to adult participants with and without dyslexia. Homophone and pseudo-homophone stimuli were included to explore whether the two groups differed in their reliance on phonological encoding. Transposed-letter stimuli, including both TL neighbours and TL non-words, measured potential orthographic impairment predicted by visuo-attentional deficit theories. The findings revealed no significant difference in response time or accuracy between the groups for the homophone and pseudo-homophone stimuli. However, dyslexics were significantly slower and less accurate in their responses to the TL stimuli than controls. Thus, dyslexics presented deficits consistent with visuo-attentional theories, but not with the phonological deficit theory.

KEYWORDS:

• Dyslexia
• lexical decision
• homophone
• transposed-letter
• orthographic
• phonological

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability

The data and code that support the findings of this study are openly available in the Open Science Framework at http://doi.org/10.17605/OSF.IO/GJP4E (https://osf.io/gjp4e/).

Additional information

Funding

This work was supported by National Institutes of Health: [Grant Number R15EY029510].