A differential-outcome effect in pigeons using spatial hedonically nondifferential outcomes.

We examined the extent to which nonhedonically different differential outcomes involving feeder location control pigeons' comparison choices in matching to sample. In Experiment 1, we showed that differential feeder location outcomes associated with each of two samples can facilitate delayed-matching accuracy. In Experiment 2, we found positive transfer following training on two matching tasks with differential feeder location outcomes when samples from one task were replaced by samples from the other task. In Experiment 3, we found that when differential-outcome expectations could no longer serve as the cues for comparison choice, sample stimuli continued to exert some control over choice of comparisons. The results indicate that differential outcomes (involving feeder location) that presumably do not differ in hedonic value are sufficient to control comparison choice. Thus, the differential hedonic value of the outcome elicited by the sample does not appear to be a requirement of the differential-outcome effect. Furthermore, these differential outcomes appear to augment matching accuracy, but they do not eliminate control by the samples.