Categorical colour perception occurs in both signalling and non-signalling colour ranges in a songbird

Although perception begins when a stimulus is transduced by a sensory neuron, numerous perceptual mechanisms can modify sensory information as it is processed by an animal’s nervous system. One such mechanism is categorical perception, in which 1) continuously-varying stimuli are labelled as belonging to a discrete number of categories and 2) there is enhanced discrimination between stimuli from different categories as compared to equally-different stimuli from within the same category. We have shown previously that female zebra finches (Taeniopygia guttata) categorically perceive colours along an orange-red continuum that aligns with the carotenoid-based colouration of male beaks, a trait that serves as an assessment signal in female mate choice. Here we demonstrate that categorical perception occurs along a blue-green continuum as well, suggesting that categorical colour perception may be a general feature of zebra finch vision. Although we identified two categories in both the blue-g...