2-DIMENSIONAL SYMMETRICAL FORM DISCRIMINATION - FAST LEARNING, BUT NOT THAT FAST

Several authors have characterized a striking phenomenon of perceptual learning in visual discrimination tasks. This learning process is sel ective for the stimulus characteristics and location in the visual fie ld. Since the human visual system exploits symmetry for object recogni tion we were interested in exploring how it learns to use preattentive symmetry cues for discriminating simple, meaningless, forms. In this study, similar to previous studies of perceptual learning, we asked wh ether the effects of practice acquired in the discrimination of pairs of shape with a specific orientation of the symmetry axis would transf er to the discrimination of shapes with different orientation of symme try axis, or to shapes presented in different areas of the visual fiel d. We found that there was no learning transfer between forms with ver y different axes of symmetry (90 degrees apart). Interestingly, howeve r, we found a transfer of learning effect to horizontally oriented sym metry axis from a condition with an axis of symmetry differing by 45 d egrees. Also it appears that some subjects took a longer time to learn than the typical ''fast learning'' paradigm would predict. Data showe d that when observers practice discrimination of meaningless symmetric forms, consistent improvement in the performance occurs. This improve ment is lasting over days, and it tends to be specific for the area of the visual field trained. We will discuss results from some of the ob servers whose learning was not ''fast'', but who actually improved wit h more practice and with large time intervals (1 day) between training sessions.