Perceptual Cues in Pure Alexia

This study provides evidence that pure alexia, or letter-by-letter reading, may be attributed to a general perceptual deficit that extends beyond an orthographic disorder. The perceptual problem may be unmasked when appropriate perceptual cues are not available to aid in the derivation of an integrated structural description. Four pure alexic patients and eight nonbrain-damaged controls participated in this study. In the first two experiments, subjects’ reading abilities were assessed on a naming latency and a lexical decision task. Experiment 3 replicated Farah and Wallace’s (1991) results that the pure alexia deficit was not specific to orthography. Experiments 4 and 5 further explored the nature of the perceptual disorder using nonorthographic stimuli. In Experiment 4, patient performance on a target detection task was unaOEected by the number of parts comprising the object but was impaired when the perceptual cue of good continuation was absent. Patient performance also declined when the perceptual cue of symmetry was not available to aid in the integration of occluded object parts in Experiment 5. Overall, the results imply that pure alexia is most likely to arise from a more general, nonorthographic deficit, and that the nature of the disorder is revealed when the perceptual context lacks strong perceptual cues.