Visual discrimination of real objects and pictures in pigeons

Pigeons were trained on two visual discrimination tasks. One task was discrimination between real objects and their photographs. Training stimuli consisted of real food (grains), photographs of food, and nonedible junk objects and their photographs. The other task was discrimination between food and nonfood using the same stimuli as those in the first task. The pigeons learned either task and showed generalization of these classifications to novel stimuli. These results suggest that pigeons can either discriminate or integrate real stimuli and their photographs. Bilateral ectostriatal lesions caused deficits in food versus nonfood discrimination, but not in object versus picture discrimination. This dissociation suggests different brain mechanisms between the two visual discriminations using the same stimuli.