Conditioned preference in humans: A novel experimental approach

Conditioned pattern preferences were induced in 20 human participants using a computerized touch screen procedure. Three abstract monochrome patterns, presented incidentally to the subject over 180 trials in the context of a counting task, were randomly assigned to one of three reinforcement contingencies. One pattern was paired with positive visual and auditory feedback together with food reward on 90% of the trials in which it was presented and with negative visual and auditory feedback together with no food reward on the other 10% of trials. The other patterns were similarly reinforced, but at ratios of 50%:50% and 10%:90% with reward and negative feedback, respectively. Subsequently, the participants preferred the "positive" pattern (that paired most often with reward) to the "negative" pattern (that paired least often with reward). Furthermore, participants did not explicitly relate their preferences to the conditioning procedure, but instead attributed them to the characteristics of the patterns themselves, indicating that subjects were not completely aware of the effects of the conditioning procedure on their subsequent behavior. (C) 1999 Academic Press.