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En Zhang, Wu Li; Visual perceptual training induces two dissociable learning effects. Journal of Vision 2014;14(10):945. doi: 10.1167/14.10.945.
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© ARVO (1962-2015); The Authors (2016-present)
Our percept of a target stimulus can be affected by stimulus context. Previous studies on perceptual learning usually focus on improvement in discrimination of the target; it is unclear whether training can also modify the interactions between the task-relevant target and the task-irrelevant context. In this study we examined the effect of training on orientation discrimination in the presence of center-surround interactions. Human subjects were trained to discriminate an orientation difference between two successively displayed stimuli. One stimulus consisted of concentric grating patches, the inner gratings at a constant reference orientation, and the outer gratings at a different orientation to induce tilt illusion on the inner gratings. The other stimulus was similar to the inner gratings except for a small difference in orientation from the reference. This design allowed for a simultaneous measure of the threshold for orientation discrimination and the magnitude of the tilt illusion based on the psychometric curve. No error feedback was given. Our data showed that not only the threshold for orientation discrimination but also the magnitude of orientation illusion gradually decreased with training. The reduction of the illusion was maintained long after training, suggesting a long-term modification of contextual influences. Although training resulted in a parallel change in orientation discriminability and illusion magnitude, no day-by-day correlation of the learning effects was found. Moreover, by independently manipulating the orientations of the inner and outer gratings and keeping their containing angle identical, we found that the improvement in orientation discriminability was specific to the orientation of the inner but not outer gratings, while the reduction in orientation illusion showed an opposite effect. These results indicate that the training induced two dissociable perceptual changes, which could engage two different processes, a local process for enhancing orientation discriminability and a global process for modifying contextual influences.
Meeting abstract presented at VSS 2014
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