Feature-positive and feature-negative learning in the rhesus monkey and pigeon.

In separate experiments four monkeys and eight pigeons were presented with displays containing one red and two green keys and displays containing three green keys. During feature-positive phases, responses to displays containing the one red and two green keys were reinforced on a fixed-ratio schedule, while responses to displays containing the three green keys were never reinforced. During feature-negative phases, only responses to the three green key displays were reinforced. For monkeys in Experiment 1, both between and within subject analyses indicated that the learning of feature-positive discriminations was superior to the learning of feature-negative discriminations. The within subject analysis further revealed that performance on a feature-positive discrimination was retarded following exposure to a feature-negative discrimination, while performance on a feature-negative discrimination was enhanced following exposure to a feature-positive discrimination. Experiment 2 replicated the essential aspects of these reversal effects in four experimental pigeons. Evidence that these reversal effects were not simply a function of time was provided by four control birds exposed to only a feature-positive or feature-negative discrimination.