ABSTRACT
Most of the research on pattern recognition in animals has concentrated on the role of static dimensions or spatial features in visual perception. The types of stimuli employed have typically been simple colored forms, more complex geometric shapes, or naturalistic photographic scenes. Single-cell recordings from the pigeon's visual system reveal that the majority of visually responsive units is optimally activated by moving stimuli. The pigeon's minimal velocity sensitivity and differential sensitivity to speed of movement have been measured psychophysically. Surprisingly, the movement thresholds obtained from pigeons are much poorer than those determined when humans are tested in comparable situations. With static shapes there is evidence that pigeons as well as humans can recognize the essential equivalence of patterns whose size or contrast has been changed. Furthermore, pigeons are capable of rotational invariance after alterations in stimulus orientation.
