Abstract
Perceptual learning in visual discrimination can be observed by monitoring an increase in an observer's ability to perform a certain task with practice. Perceptual learning has been previously linked to several different mechanisms that can account for the increase in an observer's ability: learning to perform the task it self (Anderson, Psychological Review, 94, 192, 1987), learning an optimal response strategy/adjusting criteria (Doane, Alderton, Sohn & Pellegrino, Journal of Experimental Psychology, 22, 1218, 1996), as well as changes in how the physical stimuli are perceived and processed by the observer (Gibson, 1969; Goldstone, Annual Review of Psychology, 49, 585, 1998). Observers can learn to visually fixate on areas of an image/stimuli that provide information necessary to complete their task, while avoiding areas that are not informative. This form of perceptual learning suggests a learned change in the observer's visual fixation strategy, an area of perceptual learning that has not been studied with visual hyperacuity paradigms. During training for visual hyperacuity discriminations based on small differences in the spatial frequency or orientation of suprathreshold sinusoidal gratings, observers had their eye fixations recorded. Results showed a change in fixation strategy for all observers as their experience increased and the difficulty of the discriminations increased. Observers varied in their fixation changes, as well as their final fixation points. There was a negative correlation between fixation variance and number of trials completed, but this value did not reach significance for most observers. These results suggest that observers modify their fixation strategy over time to optimize their performance on the discrimination task. This is somewhat contradicted by the observation that incorrect responses belong to the same distribution of eye fixations as correct responses.
This study was funded in part by an NIH grant to LAO, NSERC and CFI grants to DE, and a CIHR grant to AJ.