Transient deficit hypothesis and dyslexia: examination of whole-parts relationship, retinal sensitivity, and spatial and temporal frequencies.

A defect affecting the transient visual sub-system is believed to be one of the prime factors affecting reading disability. In this study, the transient deficit hypothesis was tested using the global precedence paradigm, examining retinal sensitivity, and comparing of patterns of responses to large versus small stimuli. Participants were three groups of dyslexic, chronologically age-matched, and reading age-matched children. The results revealed that although dyslexic individuals did not show any deficit in processing (a) wholes and parts (Experiment 1); (b) information in peripheral locations of the retina (Experiment 2); and (c) various sizes of the stimulus (Experiment 3); they showed a deficit in temporal processing of visual information. These findings challenge the transient deficit hypothesis in the sense that the transient sub-system has been suggested to be associated with processing of the global level, low spatial frequencies, and peripheral vision; however, they confirm that hypothesis in the sense that this visual sub-system is suggested to be associated with processing of high temporal frequencies. Transient deficit hypothesis and dyslexia: examination of whole-parts relationship, retinal sensitivity, and spatial and temporal frequencies.