Reinforcement without awareness: I. Voice level.

Although some studies have reported that reinforcement can strengthen people's behaviour without their awareness, most studies that have incorporated adequate procedures for assessing awareness have been unsuccessful. Using rigorous procedures, we report two studies designed to provide more scope for learning without awareness by making the reinforcement contingency as unobtrusive as possible. Subjects were told that the experiment was on ESP, and that they were to say which of two words the experimenter was thinking about. In fact, reinforcement was contingent on the loudness of the subject's voice when responding. Even though subjects reported no awareness of a relationship between trial outcomes and their behaviour, the probability of the reinforced responses increased significantly over trials in both experiments. These results support the view that reinforcement can occur without awareness.