Kelly, D. M., Bischof, W. F., Wong-Wylie, D. R., and Spetch, M. (2001). Detection of Glass patterns by pigeons and humans, Psychological Science, 12, 338-342.

Glass patterns have been used to examine mechanisms underlying form perception (e.g., Wilson, Wilkinson & Asaad, 1997 and Wilson & Wilkinson, 1998). The current investigation compared detection of Glass patterns by pigeons and humans and provided evidence for substantial species differences in global form perception. Subjects were required to discriminate, on a simultaneous display, a random dot pattern from a Glass pattern. Four different randomly presented Glass patterns were used (concentric, radial, parallel-vertical and parallel-horizontal). Detection thresholds were measured by degrading the Glass patterns through the addition of random noise. For both humans and pigeons discrimination decreased systematically with the addition of noise. Humans showed detection differences between the four patterns, with lowest thresholds to radial and concentric patterns and highest thresholds with the parallel-horizontal pattern. Pigeons did not show a detection difference between the four patterns. Implications for differences in neural processing of complex forms are discussed.

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