Images of conspecifics as categories to be discriminated by pigeons and chickens: Slides, video tapes, stuffed birds and live birds.

Four experiments investigated the discrimination of images of conspecifics by pigeons; in Experiment 1, chickens were also used as subjects, and images of allospecifics were also used as discriminative stimuli. In Experiment 1, chickens were successfully trained to discriminate slides of pigeons, pictures of one bird being positive stimuli and pictures of another bird being negative; and pigeons were similarly trained to discriminate slides of chickens. However, an attempt to train pigeons to discriminate slides of pigeons only succeeded with one bird out of six. Pigeons were slower to learn chicken slides, and chickens were slower to learn pigeon slides, than chickens were to learn chicken slides in a previous experiment. In Experiment 2, a dishabituation technique was used to demonstrate that pigeons readily discriminate individual live pigeons. In Experiment 3, an attempt was made to test habituation to life-size moving video images of pigeons, but these images did not elicit any natural social responses from the subject pigeons. In Experiment 4 pigeons were trained in a discrimination in which the objects to be discriminated were two different stuffed pigeons. No pigeon learned this discrimination. The experiments give some evidence that chickens are better at discriminating images of individuals than pigeons. No single feature seems to be sufficient for pigeons to discriminate between conspecifics, but the combination of features that is required remains unknown.