Pictorial same-different categorical learning and discrimination in pigeons

Two experiments examined the range of conditions over which five pigeons previously demonstrated to have a generalized same-different concept would transfer this behavior. Using two-alternative choice task that required discrimination of odd-item Different displays, in which contrasting elements were present, from Same displays, in which all of the elements were identical, these birds were transfer tested to novel display types that were outside the stimulus range of their established discriminative behavior. Experiment 1 found evidence of positive transfer for a majority of the birds to semi-realistic gray scale pictures of objects from four categories (birds, flowers, fish, and humans). Experiment 2 found evidence of positive transfer for a majority of the pigeons to realistic gray scale and color photographs of objects from sire categories (birds, flowers, cars, cats, dogs, and buildings). The results suggest these pigeons possessed a generalized rule that could be applied to novel stimuli from outside their direct experience, and add to the growing evidence that pigeons can form broadly-defined relational same-different concepts.