PERCEPTUAL LEARNING IN DYSLEXICS AND CONTROLS

Perceptual learning is considered a mechanism by which vision system automatically and implicitly improves by specific training. This mechanism is supposed to be related to attention, perception and memory functions. Although a lot of studies on dyslexics evidenced impaired motion perception and deficit in procedural learning, a lack of consensus concerned these issues. The aim of this study is to examine whether the perceptual learning would produce different patterns of results in a visual motion discrimination task in dyslexics and controls. Thirty-two subjects (9 dyslexics and 23 controls) take part in the experiment. A modified task irrelevant perceptual learning procedure is used (TIPL by Seitz and Watanabe, 2003). The procedure consists of three phases: pre-test, training and post-test. During the pretest the motion perception ability is evaluated using motion coherence test. Then, each subject is exposed to seven training sessions, in three days. The learning is mediated by subliminally pairing one selected direction with specific targets of an unrelated training task. The day after the subject motion perception ability is evaluated (post-test phase). The difference between pre and post-tests represents the implicit learning effect. A significant learning effect is found in controls, while the dyslexics subjects have lower improvement after the training. These results support the hypothesis that dyslexics have implicit learning difficulties associated to perceptual deficits.