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Nicholas M. Van Horn, Alexander A. Petrov; Practice abolishes similarity's influence on VSTM-induced interference on perception. Journal of Vision 2014;14(10):156. doi: https://doi.org/10.1167/14.10.156.
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Recent work on visual short-term memory (VSTM) has revealed that visual input is subject to modulation by the contents of VSTM. According to the sensory-recruitment model of VSTM, this interaction, and the related phenomenon of memory masking, is explained in terms of overlapping neural populations. The current study demonstrates that VSTM's influence on the current visual percept is not set by a fixed limit, but rather can be reduced with training. Method: Seventeen observers trained for six one-hour sessions to memorize the orientation of a sample Gabor and reproduce it 4.25 seconds later by rotating a match Gabor. During the retention interval, observers also completed a binary orientation-discrimination task with a target Gabor. Adaptive methods estimated discrimination psychometric functions across training sessions. In one group, the mean orientation of the memory sample during training was identical ("congruent") to the discrimination boundary. In the other group ("incongruent"), the orientations were orthogonal. Both groups completed pre- and post-tests in which the sample orientation, and therefore the congruency condition, was switched. Results: Discrimination thresholds were initially worse for incongruent than congruent trials, indicating VSTM-induced influence on perceptual representations. This difference diminished quickly with practice, and both congruency groups reached identical asymptotic performance (discrimination threshold of 7 degrees at 84% correct). Post-tests indicated that improvements on incongruent stimuli transferred almost completely to congruent stimuli, whereas improvements on congruent stimuli were almost completely specific. Discussion: These results support recent studies indicating VSTM-dependent changes in perception during the memory retention interval, and provide the first evidence that similarity-based differences in the amount of interference can be eliminated with training. The greater interference observed for incongruent stimuli challenges traditional interpretations of similarity's role in the interaction between VSTM and perceptual representations.
Meeting abstract presented at VSS 2014
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