AN INVESTIGATION OF COGNITIVE DYSMETRIA IN DEVELOPMENTAL DYSLEXIA

Abstract

An alternative to theories positing visual or phonological deficits, the “cognitive dysmetria†hypothesis proposes the aetiology of dyslexia to take the form of a general functional coordination deficit or cognitive dysmetria. The term “dysmetria†describes a general impairment in the temporal correlation of brain activity. The purpose of the current research was to investigate the empirical basis for this idea in an experimental task designed to measure simultaneity thresholds. Twenty children diagnosed with developmental dyslexia, alongside twenty, age and IQ matched controls, undertook a series of threshold determination procedures designed to measure the location of simultaneity thresholds in time and the influence of subthreshold synchrony upon perceived simultaneity. It was concluded that there was no significant difference in simultaneity thresholds for dyslexics in comparison to controls, indicating no evidence of a cognitive dysmetria. Dyslexic readers did perform significantly differently to controls on the experimental task. The results are discussed with reference to weak synchronisation and extended visual persistence in dyslexia. The possibility that the results might indicate a temporal processing deficit is also discussed.