Abstract:

PURPOSE: Perceptual learning (PL) can transfer completely to an orthogonal orientation if the latter is exposed through an irrelevant task (Zhang et al., 2010). PL thus is more likely rule-based cognitive learning. However, it is unclear why PL is orientation specific in the first place and why exposure to the transfer orientation enables learning transfer. Here we used a continuous ?ashing suppression (CFS) paradigm to answer these questions.
METHODS: Foveal orientation discrimination was always trained at one orientation. In other blocks of trials ?ashing white noise was presented to one eye, which suppressed the awareness of an orthogonal Gabor (sometimes a letter C) presented to the other eye.
RESULTS: In bottom-up orientation exposure condition, observers reported the color of a dot centered on the noise in the dominant eye, without knowing the presence of the subconscious orthogonal Gabor in the non-dominant eye. This bottom-up exposure produced partial transfer. In a top-down “exposure” condition, observers were required to report, or guess is they had to, whether an orthogonal Gabor/letter-C was presented to the non-dominant eye even though it was suppressed by the ?ashing noise in the dominant eye. However, during actual experiment neither the Gabor nor the letter C was presented. This top-down "exposure" also induced partial transfer. In a third condition, when observers performed the Gabor/C task and the orthogonal Gabor was actually present, this combined bottom-up and top-down exposure induced complete learning transfer.
CONCLUSIONS: These results suggest that learning speci?city may result from under-activations of untrained visual neurons due to insufficient bottom-up stimulation and/or top-down attention during training. High-level perceptual learning thus may not functionally connect to these neurons for learning transfer. 

Key words: perceptual learning, under-stimulation, specificity, transfer