Abstract
The purpose of this experiment was to study whether conditioned diminution of the unconditioned response (UR) is a phenomenon with an associative basis. Twenty-five subjects received discrimination training with an interval between conditioned stimulus (CS) and unconditioned stimulus (US) of 5 s (differential conditioning group). The same stimuli were presented to another twenty-five subjects, but in an explicitly uncorrelated manner (non-conditioning group). After the acquisition phase, participants of each group were tested with seven presentations of CS+/US and CS-/US. The results of the acquisition phase showed that the UR amplitude was lower in the differential conditioning group than in the non-conditioning group. In the testing phase, CS+/US presentations elicited URs of lower amplitude than CS-/US in the differential conditioning group, but not in the non-conditioning-group. These findings are discussed as a result of expectancy and associative effects of conditioning processes.
