Stimulus representations in human Pavlovian conditioning: Implications of missing negative transfer across response systems

Three Pavlovian conditioning experiments with human participants are report ed, which investigated whether common or separate stimulus representations are involved in solving nonlinear discrimination tasks in different respons e systems. In our experiments we made use of a negative transfer effect bet ween positive and negative patterning. Experiment 1 specified the condition s under which such a negative transfer effect occurs in human eyelid condit ioning. Experiments 2 and 3 investigated whether a similar effect also occu rs if two response systems-the eyelid and the skin conductance response sys tem-are trained with trials of both types being randomly interleaved. The p resence or absence of a negative transfer effect indicates whether or not t he stimulus representations involved in the two conditioning processes over lap. The findings are discussed within the framework of a neuropsychologica l model of hippocampal function. The results suggest that the representatio ns are distinct and thus support the idea of acquired equivalence and disti nctiveness of stimulus representations.