The perception of Glass patterns by starlings (Sturnus vulgaris).

Glass patterns are structured dot stimuli used to investigate the visual perception of global form. Studies have demonstrated that humans and pigeons differ in their processing of circular versus linearly organized Glass patterns. To test whether this comparative difference is characteristic of birds as a phylogenetic class, we investigated for the first time how a passerine (starlings, Sturnus vulgaris) discriminated multiple Glass patterns from random-dot stimuli in a simultaneous discrimination. By examining acquisition, steady-state performance, and the effects of diminishing global coherence, it was found that the perception of Glass patterns by 5 starlings differed from human perception and corresponded to that established with pigeons. This suggests an important difference in how birds and primates are specialized in their processing of circular visual patterns, perhaps related to face perception, or in how these highly visual animals direct attention to the global and local components of spatially separated form stimuli.