Abstract
Background: The relationship between awareness and associative learning is a key controversial issue that remains to be elucidated. An experiment was designed to assess associative learning with and without perceptual awareness. Method: Participants received repeated trials of two compatible stimuli sequences (S1A → S2A and S1B → S2B), where S1 was a masked stimulus, and S2 an imperative stimulus for a reaction time (RT) task. After the acquisition phase, some probe trials of incompatible stimuli sequences (S1A → S2B and S1B → S2A) were inserted among the compatible sequence trials during two testing sessions. Subsequently, subjects were classified as perceptually aware or perceptually unaware by means of a forced-choice identification task that was administered at the beginning and end of the experiment. Results: The results showed perceptually unaware participants responded faster to compatible than to incompatible stimuli sequences. However, no priming effect was observed in aware participants. Conclusions: These results are discussed in terms of an S-R associative mechanism and provide strong evidence of unconscious associative learning.
