The fundamental equation of the rational theory of categorization specifies the calculation of the posterior probability that an instance with features F comes from category k were P(k) is the prior probability of being in category k and P(f|k) is the conditional probability of displaying feature f given that the object comes from category k. This quantity can basically be thought of as a match to a category based on feature overlap. We use this equation in the visual interface to determine the identity of an object.