Abstract
Color is a prime example of categorical perception, yet it is still unclear why and how color categories emerge. The key questions revolve around to what extent perceptual and linguistic processes determine categories. While prelinguistic infants and animals appear to treat color categorically, several recent attempts to model category formation have successfully utilized communicative concepts to predict color categories. Considering this apparent discrepancy, we take a different approach. Rather than modeling categories directly, we focus on the potential emergence of color categories as the result of acquiring basic visual skills. For this, we investigated whether color is represented categorically in a convolutional neural network (CNN) trained to recognize objects in natural images. We systematically trained novel output layers to the CNN for a color classification task, and found that clear borders arise between novel (non-training) colors that are largely invariant to the training colors. We confirmed these border locations by searching for the optimal border placement using an evolutionary algorithm that relies on the principle of categorical perception. Our findings also extend to stimuli with multiple, colored, words of varying color contrast, as well as colored objects with larger colored surfaces. These results provide strong evidence that color categorization can emerge with the development of object recognition.
Significance statement The origin of color categories has been a controversial topic for a long time, the key question being to what extent perceptual and linguistic processes determine categories. Typically, this has been evaluated by modeling the shape of categories directly. Here, we take a very different approach and evaluate categorization in a neural network built for recognizing objects in natural scenes. Interestingly, the network appears to build a categorical representation of color as a side effect of learning to classify objects. This shows categorization may be driven by acquiring basic visual skills, particularly those pertaining to objects.
Competing Interest Statement
The authors have declared no competing interest.