Examination of hierarchical form perception in African grey parrots (Psittacus erithacus).

The perception of objects is a challenging task that requires recognizing visual elements and integrating them into a whole. While human vision prioritizes attention to the overall configuration, data from other species suggests this bias towards global form perception is not universal. Studies with pigeons indicate preferential attention to local details when both local and global information may be diagnostic, but studies with other bird species are more limited. To examine whether this local bias is class-wide or potentially species-specific, we studied whether African grey parrots (Psittacus erithacus) have a bias towards local elements or the global configuration when processing Navon-like hierarchical form displays. Two parrots were tested using a computerized touch-screen two-alternative choice task that presented displays that were local-relevant or global-relevant. The results of several successive acquisition phases suggest that these parrots have no local or global bias, indicating differing evolutionary or ecological drives for visual processing among avian species.