Animal Cognition

, Volume 11, Issue 4, pp 569–585 | Cite as

The use of perceptual features in categorization by orangutans (Pongo abelli)

Original Paper


The extent to which categorization of natural classes in animals reflects a generalization based on perceptual similarity versus an abstract conceptual representation remains unclear. Here, two experiments were conducted to identify the perceptual features used by orangutans when categorizing pictures. In Experiment 1, subjects were trained and tested for transfer on a concrete discrimination (gorillas or orangutans vs. other primates). Analysis of performance on both positive and negative exemplars revealed that performance was best on photos with faces, particularly close-ups. Moreover, error trials did not seem to reflect instances of mistaken identity, but rather, exemplars that may have been distracting for other reasons, such as novel coloration or morphology. In Experiment 2, photos were modified to test the effects of various features. Color modifications caused the biggest decrease in performance, and eye modifications also affected performance deleteriously. Therefore, two perceptual features, namely eye regions and color, played a key role in subjects’ ability to categorize. However, performance based on an underlying concept cannot be ruled out, because both of these features are highly relevant in terms of defining category membership. Although a subset of features was identified as playing a key role in categorization, these features differed depending on whether feature-use was studied indirectly, as in Experiment 1, or directly, as in Experiment 2.


Categorization Concepts Perceptual features 

Supplementary material

10071_2008_148_MOESM1_ESM.doc (1.6 mb)
S1. Samples of photo modifications used in Experiment 2 (DOC 1.55 Mb)


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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.Department of PsychologyYork UniversityTorontoCanada

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