Investigating Binding Deficits in Dyslexia

Abstract

Working Memory deficits have been well-documented as a significant characteristic in defining ‘dyslexia’ (McLoughlin, Fitzgibbon, & Young, 1994). Possible visual working memory impairment in dyslexics makes it difficult to remember visual information in the form of features or whole objects, over a short period of time. We investigated whether these impairments could be explained by the inability to create or maintain relevant associations between related pieces of information or by a plausible smaller visual working memory capacity. We also addressed the debate of whether visual working memory capacity was defined by individual features or whole object representations, for both non-dyslexic and dyslexic readers (Luck & Vogel, 1997; Wheeler & Treisman, 2002). Using two experiments of recognition and recall, we examined how dyslexic and non-dyslexic readers are able to form effective bound object representations by manipulating the number of features present per item that had to be subsequently remembered for the next test. Results from the mixed ANOVA analyses demonstrated that non-dyslexic and dyslexic readers are both more likely to encode information as whole objects rather than multiple features. Additionally, dyslexic readers exhibited a possible smaller visual working memory capacity than the non-dyslexic readers. This study elucidates processes underpinning visual recognition performance of non-dyslexic readers and pinpoints the impaired areas of dyslexic readers. We discuss our findings with reference to visual processing deficit theory of dyslexia, suggesting that the decline in memory performance in dyslexic readers are at least, partly due to the associative impairments.