Picture perception in monkeys and pigeons: transfer of rightside-up versus upside-down discrimination of photographic objects across conceptual categories.
Masako Jitsumori, Tetsuro Matsuzawa
monkeys and pigeons were trained to discriminate between normally oriented full frontal pictures of humans and upside-down reversals of the same pictures as stimuli. monkeys displayed a high level of transfer to the new pictures of full frontal and rear views of humans and silhouettes, but failed to transfer to the close-up and far human faces. pigeons showed poorer transfer to the silhouettes and higher transfer to the far human faces than did monkeys. further transfer tests were performed with non-human pictures, including monkeys, birds, mammals, and man-made objects. pigeons failed to transfer to the non-human pictures. this indicates that the pigeons had learned to classify the pictures based on some concrete features specific to the humans and that the transfer to the new versions of human pictures could be explained by simple stimulus generalization based on perceptual similarity. two out of four monkeys did transfer fairly well to the non-human pictures, except for the man-made objects. high levels of transfer to the non-human natural pictures suggested that the monkeys classified the pictures on the basis of the orientation of objects represented by the pictorial displays.