Implicit Learning: a stimulus-response framework.

Several aspects of implicit learning have already been explored since Reber first defined it in 1967, from sequence to statistical learning and from artificial grammar learning to contextual cueing in visual search. In the current study, our aim was to investigate a new facet of implicit learning based on a stimulus-response association. Particularly, the participants had to report the motion direction of a single patch of dots, either left/right in a first experiment or top/down in a second one. In each trial the patch can be of three different colors, and unbeknownst to the participants, two of these colors were always associated with the same direction/response, while the third color was completely uninformative. In the first experiment, using the performance of the participants trial by trial, we fitted a Bayesian model in order to assess the level of implicit learning of information conveyed by the color. In the second experiment, using the same model, we disentangled the association between color and motion, and color and response, in order to test which association was actually learnt by the participants. The results highlight, despite a high interindividual variability, a robust implicit learning of the stimulus-response association, both in the first and second experiment. In addition, the second experiment shows how the participants independently learn stimulus-response and stimulus-stimulus associations. Future studies will focus on the neural correlates of this type of learning, and on the causes of such variability between subjects.