Color-dominant processing in pigeon object recognition: behavioral and entopallial evidence from redundant-cue transfer tasks

Birds possess remarkable visual object classification abilities. Objects in nature often contain multiple redundant cues (e.g., color and shape). Previous work has shown that pigeons prefer color over shape for target classification, but it remains unknown whether they rely primary on color or whether shape also provides discriminative information when both cues are available. To address this, we trained pigeons on single-cue (color-only or shape-only) discrimination tasks and then transferred them to multi-cue (color + shape) tasks, while simultaneously recording neural responses from the entopallium. Behaviorally, shifting from single-color to multi-cue produced no change in recognition accuracy, whereas shifting from single-shape to multi-cue significantly improved accuracy. This pattern suggests that color provided the primary behavioral driver, with shape adding limited detectable benefit under these specific conditions. Neurophysiologically, most recording sites in the entopallial showed stronger local field potential responses to color than to shape cues, and local functional connectivity was less dense under multi-cue than single-cue images. Together, these findings suggest that, under the present redundant-cue paradigm, pigeons exhibited a preferential reliance on color over shape for object recognition a processing bias that may reflect an efficient strategy when one cue is sufficient for accurate classification. These findings contribute to our understanding of how birds process redundant visual information under conditions of cue redundancy.