Are task irrelevant faces unintentionally processed? Implicit learning as a test case.

Faces are one of the most important signals for reading people's mental states. In sync with their apparent "chronic" (cross-situational) relevance, faces have been argued to be processed independently of the task one is currently performing. Many of these demonstrations have involved "capture of attention" or increased interference by faces functioning as distractors. Here we ask whether multiple repetitions of task irrelevant faces leave a trace in the system. Specifically, we tested whether repeating structures instantiated by task irrelevant faces are unintentionally or implicitly learned. Our findings indicate that although faces are indeed unique in that they are the only stimulus found to lead to implicit learning of complex rules when irrelevant, such learning is small in magnitude. Although these results support the conjecture that task irrelevant faces are processed, the functional significance of this learning needs to be assessed.