Differential outcome effects in pavlovian biconditional and ambiguous occasion setting tasks.

Three experiments with rats explored the differential outcome effect (DOE) using a pavlovian magazine approach conditioning preparation. Experiment 1 compared groups trained on a biconditional discrimination (AX+, AY-, BX-, BY+) with differential or nondifferential outcomes, and Experiment 2 examined this using an ambiguous occasion setting task (e.g., AX+, X-, Y+, AY-). In both experiments, subjects trained with differential outcomes learned the tasks better than subjects trained with nondifferential outcomes. Furthermore, subjects given differential outcome training learned the positive occasion setting component of the ambiguous task more efficiently than the negative occasion setting component, although both were enhanced by differential outcome training. Experiment 3 demonstrated that the ambiguous occasion setting task was reversed more readily when the target-outcome relations (as opposed to the modulator-outcome relations) were maintained during the reversal phase. These data suggest that an acquired distinctiveness effect may be responsible for the DOE in pavlovian learning.