EFFECTS OF MISCUING ON PAVLOVIAN CONDITIONED RESPONDING AND ON PROBE REACTION-TIME

Two experiments examined the effect of the miscuing of an unconditione d stimulus on Pavlovian conditioned responding. In Experiment 1 (N = 3 2), subjects received 12 CS+-US and 12 CS- presentations followed, in the experimental group, by a CS--US pairing (miscuing) on Trial 25 and a CS+-US pairing on Trial 26. For the control group, Trial 25 consist ed of a CS--alone presentation and Trial 26 consisted of a CS+-US pair ing. Visual stimuli (geometric shapes) of 8-s duration served as CSs, and a 1-s burst of white noise (100 dBA) was used as the US. Both elec trodermal activity and a continuous measure of US expectancy were obta ined. Expectancy of the US was significantly lower in the experimental group than in the control on the CS+-US trial which followed miscuing , whereas electrodermal responses to the US were significantly larger. However, first- and second-interval responses during CS+ on this tria l were not influenced by miscuing. Experiment 2 (N = 64) employed the same stimuli and procedures as used in Experiment 1, but the dependent measure was reaction time to a probe stimulus presented either early (300 ms) or late (7500 ms) during some CSs+ and some CSs-. During the acquisition phase, probe reaction time was slower during CS+ than duri ng CS- regardless of probe position. Moreover, reaction time to probes presented during CS+ on the trial which followed miscuing was slower in the experimental group than in the control irrespective of probe po sition. Although not all findings were as predicted, the present resul ts suggest that a CS-US pairing disrupted the association between CSand the US. This effect of US miscuing is difficult to interpret withi n the framework of current theories of Pavlovian conditioning.