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Dorita H. F. Chang, Zoe Kourtzi, Andrew E. Welchman; Asymmetric transfer of perceptual learning between coarse and fine depth discriminations. Journal of Vision 2011;11(11):334. doi: 10.1167/11.11.334.
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© ARVO (1962-2015); The Authors (2016-present)
A prominent view in the literature posits that coarse and fine binocular disparities are processed by the dorsal and ventral pathways of the brain, respectively. However, neurophysiological data have shown that the contribution of dorsal areas to coarse depth discriminations can be altered through training on fine depth discriminations. Here, we use human psychophysics to investigate the perceptual learning of depth discriminations and test whether learning of fine depth discrimination alters performance on a coarse depth task, and vice versa. Observers were presented with random-dot stereograms depicting a central plane (target) within a background (surround) and judged whether the target was nearer or farther than the surround. Task difficulty was manipulated by (i) varying the percentage of signal dots (Coarse task), or (ii) the disparity difference between the target and the surround (Fine task). Half of the observers were trained on 840 trials with feedback on the Coarse task, the other half on the Fine task. All participants were tested on both tasks before and after training without feedback. The results show that training improves performance in the depth tasks, but not in an untrained, control (orientation discrimination) task. Importantly, we show that training on the Fine task leads to substantial improvements on the Coarse task, with participants improving by 70% of the total measured under dedicated training on the Coarse task. In contrast, when observers were trained on the Coarse task, we observed only 28% learning on the Fine task. These results demonstrate asymmetric transfer of learning between coarse and fine depth discriminations – a pattern that may reflect differences in the mechanisms recruited by the two tasks. We suggest that training on the fine task may enhance the representation of depth features, while training on the coarse task may enhance signal-to-noise processing, but have limited influence on feature representations.
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