title: Generalization of visual shapes by flexible and simple rules.
abstract: Rules and similarity are at the heart of our understanding of human categorization. However, it is difficult to distinguish their role as both determinants of categorization are confounded in many real situations. Rules are based on a number of identical properties between objects but  these correspondences also make objects appearing more similar. Here, we introduced a stimulus set where rules and similarity were unconfounded and we let participants generalize category examples towards new instances. We also introduced a method based on the frequency distribution of the  formed partitions in the stimulus sets, which allowed us to verify the role of rules and similarity in categorization. Our evaluation favoured the rule-based account. The most preferred rules were the simplest ones and they consisted of recurrent visual properties (regularities) in the stimulus  set. Additionally, we created different variants of the same stimulus set and tested the moderating influence of small changes in appearance of the stimulus material. A conceptual manipulation (Experiment 1) had no influence but all visual manipulations (Experiment 2 and 3) had strong influences  in participants' reliance on particular rules, indicating that prior beliefs of category defining rules are rather flexible.
authors.affiliation: Laboratory of Experimental Psychology, University of Leuven (K.U. Leuven), Tiensestraat 102, P.O. Box 3711, B-3000 Leuven, Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Ons
authors.forename: Johan
authors.initials: J
authors.lastname: Wagemans
mesh_terms: D000293:Adolescent; D003210:Concept Formation / Q000502:physiology*; D003661:Decision Support Techniques; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D055815:Young Adult