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Lin-Juan Cong, Jun-Yun Zhang, Cong Yu; Sequence is necessary for multi-stimulus perceptual learning. Journal of Vision 2013;13(9):561. doi: https://doi.org/10.1167/13.9.561.
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Perceptual learning occurs when multiple stimuli are presented in a fixed order, but not in a random order (roving). But learning can escape roving disruption when each roving stimulus is given a letter tag (i.e., A-B-C-D) (Zhang et. al, PLoS Biology, 2008). Since these letters carry both identity and sequence information, here we investigated which information in stimulus tagging really helps learning with stimulus roving. (1) First we replicated the stimulus tagging effect by assigning four roving contrasts (0.2, 0.3, 0.47, and 0.63) each a number tag (i.e., 1-2-3-4). The number tags also contained both identity and sequence information. Significant learning of contrast discrimination was evident (post/pre-training threshold ratio (PPR) = 0.82±0.05, P=0.010) after five sessions of training. (2) When stimulus tags changed to Greek letters (i.e., δ-ω-λ-θ) that had unfamiliar alphabetic sequence for Chinese observers, learning was disabled by stimulus roving (PPR = 0.94±0.04, P=0.089). (3) Jittering inter-trial intervals (ITI) did not affect learning with number tags (PPR = 0.83±0.07, p=0.041), in contrast to previous results that jittering ITI interrupted learning of multiple contrasts in a fixed order. (4) For the same four contrasts that were each assigned an orientation tag (36°-81°-126°-171°) and presented either with roving or with a clockwise order, contrast learning was evident with a stimulus order (PPR = 0.79±0.13, P=0.049), but was absent with roving (PPR = 0.99±0.08, P=0.29). These results indicate that it is the semantic sequence information in letter or number tagging that helps learning with stimulus roving. Stimulus tags, such as orientation and Greek letters (to Chinese) that carry no sequence information, are ineffective. Unlike stimulus order, the semantic sequence is strong enough that it cannot be interrupted by ITI jittering (no rhythm). These and our previous results together demonstrate that sequence is necessary for multi-stimulus learning to occur.
Meeting abstract presented at VSS 2013
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