CATEGORY DISCRIMINATION OF ARTIFICIAL POLYMORPHOUS STIMULI BASED ON FEATURE LEARNING

Pigeons and humans were trained to discriminate between sets of artificial stimuli defined by a 2-out-of-3 polymorphous concept. Stimuli containing any 2 of 3 positive or negative features were used for training, In Experiment 1, pigeons showed complete transfer to stimuli with all 3 positive or negative features and even to stimuli that had 1 of the 3 features replaced with a novel feature. In contrast, humans failed to show transfer to those stimuli. By using a selective reversal procedure for pigeons, Experiment 2 revealed that functional equivalence was not formed among either the stimuli or the features. Experiment 3 examined how pigeons integrate information from several distinct features to determine the response to any given stimulus. An additive rule and a combination rule were suggested to account for category discrimination by pigeons.