Dyslexia Research Today is a free monthly online journal that collates and summarizes the latest research about Dyslexia, including details on learning, reading, education, teaching, treatment.

Use of the Hermann grid illusion in the measurement of contrast perception in dyslexia.

Gilchrist JM, Pierscionek BK, Mann WM

Department of Optometry, University of Bradford, Richmond Road, Bradford, BD7 1DP West Yorkshire, UK. j.m.gilchrist@bradford.ac.uk

We measured contrast thresholds for perception of the Hermann grid illusion, using different contrast polarities and mean luminances, in dyslexics and non-dyslexics. Both groups of subjects gave significantly lower thresholds with grids having dark squares and light paths, but there was no significant threshold difference between groups. Perceived strength of illusion was also measured in grids at suprathreshold contrast levels. Dyslexics perceived the illusion to be significantly stronger than non-dyslexics when the grid had light paths and low luminance.

Published 1 December 2004 in Vision Res, 45(1): 1-8.
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