Adult Dyslexics’ Visuo-Spatial Serial Memory: Evidence of Intact Non-Verbal Encoding?

Whilst research consistently shows that dyslexic participants show performance deficits on a number of serial recall (SR) tasks there has been conflicting evidence about dyslexics' ability to perform visuo-spatial tasks; an inconsistency often attributed to differential task demands (Smith-Spark & Fisk 2007). Also, on different visuo-spatial tasks it is possible that participants use verbal encoding strategies to facilitate recall, which then compromises comparisons of dyslexic and non-dyslexic performance. We employed a visuo-spatial task that has been shown to minimise reliance on verbal-labeling of stimuli, and can therefore be considered a pure test of visuo-spatial SR memory. This task involves the sequential presentation of seven dots in quasi-random locations on a blank screen. The difficulty of the task can be varied by increasing the joint action of length of the path described by the sequence of dots and number of path crossings in the to-be-remembered sequence (Jones, Farrand, Stuart & Morris, 1995; Parmentier and Andres 2006). In the current study, dyslexic and non-dyslexic visuo-spatial SR was compared across 4 levels of task difficulty.