Unconscious Knowledge of Rewards Guides Instrumental Behaviors via Conscious Judgments

Abstract

The demonstration of unconscious instrumental conditioning (i.e., unconsciously learning to choose stimuli that lead to rewards) is central for the tenet that unconscious learning supports human adaptation. Recent studies, using reliable subliminal conditioning procedures, have found evidence against unconscious instrumental conditioning. The present preregistered study proposes an alternative paradigm, in which unconscious processing is stimulated not by the subliminal exposure of the predictive (conditioned) stimuli, but by employing predictive regularities that are complex and difficult to detect consciously. Participants (N = 211) were exposed to letter strings that, unknown to them, were built from two complex artificial grammars: an “rewarded’’ or a “non-rewarded” grammar. On each trial, participants memorized a string, and subsequently had to discriminate the memorized string from a distractor. Correct discriminations were rewarded only when the identified string followed the rewarded grammar, but not when it followed the non-rewarded grammar. In a subsequent test phase, participants were presented with new strings from the rewarded and from the unrewarded grammar. Their task was now to directly choose the strings from the rewarded grammar, in order to collect more rewards. Employing a trial-by-trial awareness measure widely used in implicit learning, we found that participants accurately choose novel strings from the rewarded grammar when they had no conscious knowledge of the grammar. The awareness measure also showed that participants were accurate only when the unconsciously learned grammar led to conscious judgments. The present study provides an alternative to subliminal conditioning paradigms and shows evidence for unconscious instrumental conditioning.