Abstract
We trained pigeons to peck one button in response to arrays comprising 16 identical icons (Same arrays) and a different button to arrays comprising 16 different icons (Different arrays). This task required the pigeons to classify collections of icons in terms of their variability: “low” for Same arrays and “high” for Different arrays. Previous research has demonstrated that pigeons can learn this discrimination and that behavior is a function of the categorical entropy of the items. In the present pair of experiments, we examined a perceptual account of this behavior. In Experiment 1, we upset the spatial regularities of the displays by jittering the icons — randomly displacing each icon in order to create visual disorder. The pigeons' discriminative performance was completely unaffected by jittering. In Experiment 2, spatial regularities were disturbed by randomly rotating the icons within a display. Again, no disruption in discriminative performance was observed. Despite the absence of any behavioral consequences of our manipulations, a spatial frequency analysis of the displays clearly revealed that a broad range of frequencies was disrupted by our manipulations. These and other findings suggest that pigeons treat the 16 icons as either same or different despite changes in the spatial organization or orientation of the icons.