Visual Temporal Processing in Dyslexia and the Magnocellular Deficit Theory

The Need for Speed?

Gregor M T McLean*, Geoffrey W. Stuart, Veronika Coltheart, Anne Castles

*Corresponding author for this work

Research output: Contribution to journalArticle

38 Citations (Scopus)


A controversial question in reading research is whether dyslexia is associated with impairments in the magnocellular system and, if so, how these low-level visual impairments might affect reading acquisition. This study used a novel chromatic flicker perception task to specifically explore temporal aspects of magnocellular functioning in 40 children with dyslexia and 42 age-matched controls (aged 7-11). The relationship between magnocellular temporal resolution and higher-level aspects of visual temporal processing including inspection time, single and dual-target (attentional blink) RSVP performance, go/no-go reaction time, and rapid naming was also assessed. The Dyslexia group exhibited significant deficits in magnocellular temporal resolution compared with controls, but the two groups did not differ in parvocellular temporal resolution. Despite the significant group differences, associations between magnocellular temporal resolution and reading ability were relatively weak, and links between low-level temporal resolution and reading ability did not appear specific to the magnocellular system. Factor analyses revealed that a collective Perceptual Speed factor, involving both low-level and higher-level visual temporal processing measures, accounted for unique variance in reading ability independently of phonological processing, rapid naming, and general ability.

Original languageEnglish
Pages (from-to)1957-1975
Number of pages19
JournalJournal of Experimental Psychology: Human Perception and Performance
Issue number6
Publication statusPublished - Dec 2011

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