Developmental dyslexia affects a large fraction of children with normal intelligence, vision and motivation. It appears as difficulty in reading and spelling, confusion in recognizing the orientation of letters and the orders of letters in words. All children suffer left-right and orientation confusions and recently it has been shown that all adults do as well. This project tests several ideas about why dyslexics, young children, and adults all have such great difficulties with visual perceptions involving orientation and mirror-image relationships. The role of cerebral hemispheric specialization in visual functions and the exchange of information between hemispheres will be assessed using, as a primary measure, the response times associated with various discriminations and judgments. Studies will determine the stimulus characteristics which lead to mirror-image discrimination confusions and the relation of such difficulties in normal adult subjects, to those reported for dyslexics and normal children.