Meeting Abstract
Color stimuli vary continuously, but increasing evidence suggests that color perception can be categorical. Categorical perception is a mechanism by which a perceptual system sorts continuous variation into discrete categories. Two hallmarks of categorical perception are 1) that different stimuli falling on the same side of a perceptual boundary are labeled as belonging to the same category and 2) stimuli falling on different sides of the boundary are discriminated more readily as compared to stimuli that differ by a similar physical magnitude falling within the same category. We have shown previously that female zebra finches (Taeniopygia guttata) categorically perceive colors along an orange-red continuum that aligns with the carotenoid-based coloration of male beaks, an important assessment signal in the context of mate choice. Here, we test for categorical perception along a blue-green color range, which has no known signaling function in this species, to ask whether categorical perception is specific to signaling coloration or is a general feature of avian color perception. We trained birds to search for food underneath bicolor discs and then tested for categorical perception by varying the difference between the two colors of the disc. We used a set of equiluminant colors that an established model of avian color discrimination predicts to be approximately equally discriminable from one another. Labeling trials identified the location of potential perceptual boundaries, and discrimination trials then tested for enhanced discrimination between versus within putative categories. Together, these trials show that female zebra finches exhibit categorical perception of a blue-green continuum, but with categories that are less well-defined than those observed in the orange-red range.
