EXPLICITLY-UNPAIRED AND TRULY-RANDOM CS?CONTROLS IN HUMAN CLASSICAL DIFFERENTIAL AUTONOMIC CONDITIONING

The conventionally used explicitly-unpaired CS– (euCS–) of the differential conditioning paradigm, a stimulus which is negatively correlated with the US, may generate inhibition and hence be an inappropriate control for CS+ conditioning. An implication of this possibility is that the CS+:euCS– performance difference should exceed the difference between CS+ performance and performance to a truly-random CS– (trCS–), a stimulus which is uncorrelated with US occurrence. This implication was tested in a 5-sec delay conditioning skin resistance response study (Exp. I, N = 32) and an 8-sec delay conditioning plethysmographic digital pulse volume response study (Exp. II, N = 48). While highly reliable discrimination between CS+ and the two control CSs (euCS– and trCS–) was obtained in both experiments, neither experiment yielded the outcome expected from the position that euCS– generates inhibition.