Effects of geon deletion, scrambling, and movement on picture recognition in pigeons.

E. A. Wasserman, K. Kirkpatrick-Steger, L. J. Van Hamme, and I. Biederman (1993) demonstrated that scrambling an object's parts or "geons" (I. Biederman, 1987) produced marked reductions in the pigeon's picture recognition accuracy, indicating that discriminative responding to pictures is controlled by more than simple particulate features. The present effort was designed to further assess the contribution of various stimulus attributes to picture perception. Four pigeons were trained to discriminate 4 line drawings of human-made objects. Subsequent tests revealed that (a) the spatial organization of the geons was a major contributor to picture recognition; (b) the individual geons were also important, with different pigeons demonstrating control by different subsets of geons; (c) recognition of the training drawings was positionally invariant; and (d) the points where the geons contacted one another were largely unimportant for picture recognition. The results provide further support for the notion that pigeons perceive both global and local aspects of complex stimuli in much the same way as do humans.