Is Stimulus-Stimulus Pairing Sufficient to Produce Conditional Discriminations?

The purpose of the present study was to investigate the sufficiency of stimulus-stimulus pairing in establishing conditional discriminations in adult humans. The task involved learning 32 different conditional discriminations. During training, a correct pair of sample and comparison stimuli was presented after the subjects made a sample-observing response but before (prompt) or after (feedback) the subjects made a comparison-selection response. During testing, the same conditional relations were presented without prompting or feedback to assess the development of conditional relations among the stimuli. Despite the fact that accuracy on prompt trials was quite high from the beginning of training, accuracy on prompt trials dropped substantially during the test conditions for three out of four subjects. By contrast, accuracy on the feedback trials was well maintained under test conditions. These results suggest that, in this preparation, the contemporaneous presentation of experimenter-designated correct sample and comparison stimuli is not sufficient and that some other factors may have played an important role in the establishment of conditional discriminations.