Explicit and implicit learning in motion discrimination tasks

Perceptual learning has been studied as a mechanism by which people automatically and implicitly learn. Alternatively, learning can occur explicitly mediated by conscious feed-back which controls and guides the subjects'(tm) performance. The aim of this study was to examine whether the explicit and implicit learning could produce different patterns of results in a visual motion discrimination task. We exposed 12 participants to four different sessions. A preliminary training session consisted of 120 trials of motion discrimination task repeated three times in different days to measure the explicit learning. The subject had to discriminate among 4 directions in motion test presented at 10% of coherence (considered as parathreshold). A pre-test in which the baseline was evaluated by the correct responses average in the motion discrimination task for each direction. The implicit learning session was tested using the classic paradigm of task-irrelevant perceptual learning (TIPL) (Seitz and Watanabe, 2003) in which learning was mediated by subliminally pairing one selected direction with specific targets of an unrelated training task. This phase consisted of 120 trials repeated 7 times in three days. After that a post-test similar to the pretest indicated the implicit learning effect. In the explicit learning the improvement is relatively poor and not significant. In the implicit learning the effect was clearly significant for the trained direction, while the subjects did not improve their performances in the other directions. These results of the stronger learning effect obtained in TIPL suggest that visual motion learning can benefit more from direct lower level processing then from mediated attention mechanisms related to explicit learning.