Spatial-frequency- and contrast-dependent visible persistence and reading disorder: no evidence for a basic perceptual deficit.

The aetiology of dyslexia is still unclear, the most widely and controversially discussed theory is the magnocellular deficit hypothesis. One of the first and most influential paradigms used to investigate this visual deficit in dyslexia is the visible persistence (VP). However results on VP are decisively influenced by the method measuring VP. Lovegrove et al. (1986) repeatedly found a longer VP in reading disabled children which is significantly influenced by spatial frequency and contrast. However, these results were not investigated with the same method to date. Seventy-six unselected 2nd grade students (41 boys, 35 girls) of a rural primary school were investigated with an identical experimental design comparable to the Lovegrove et al. (1986) studies. Comparing reading disabled (n = 17) with controls (n = 34) no evidence for a longer VP in the reading disabled group was found. Additionally, correlation analysis revealed no evidence for a significance of VP for spelling, phoneme awareness and speech discrimination. This study does not encourage either a magnocellular nor parvocellular deficit in dyslexia.