Literal dyslexia, the inability to read letters within a word which itself could be read, was analysed in two patients. Their impairment was found not to be specific to letters but to stimuli in which more than one item of the same category was simultaneously present in the visual field. Thus a letter surrounded by numbers could be read more easily than if surrounded by other letters. Explanations in terms of visual disorientation or implicit response interference were rejected. It is suggested that their impairment arises from a specific defect at the level at which visual input is selected for meaningful analysis.
