Similarity and discrimination in human Pavlovian conditioning.

We report three Pavlovian eyelid conditioning experiments with humans, designed to experimentally decide between elemental and configural learning theories. We used two different designs originally proposed by Redhead and Pearce (1995). In Experiments 1 and 2, three stimulus elements, A, B, and C, were presented in all possible combinations. All patterns were reinforced except for pattern ABC (A/B/C+, AB/AC/BC+, ABC-). According to elemental learning theories, response proportions on A/B/C+ trials should be smaller than on AB/AC/BC+ trials, whereas configural learning theory makes the opposite prediction. The results confirmed neither prediction. In Experiment 3, the A/B/C+, AB/AC/BC+, and ABC- trials were interspersed by D/E/F-, DE/DF/EF-, DEF+ trials. Again, neither prediction was confirmed. We suggest a modification of configural learning theory as a possible explanation of our results.