Animal Cognition

, Volume 1, Issue 1, pp 25–35 | Cite as

Perception of shape from shading in chimpanzees (Pan troglodytes) and humans (Homo sapiens)

  • Masaki Tomonaga
Original article


The perception of shape from shading was tested in two chimpanzees (Pan troglodytes) and five humans (Homo sapiens), using visual search tasks. Subjects were required to select and touch an odd item (target) from among uniform distractors. Humans found the target faster when shading was vertical than when it was horizontal, consistent with results of previous research. Both chimpanzees showed the opposite pattern: they found the target faster when shading was horizontal. The same difference in response was found in texture segregation tasks. This difference between the species could not be explained by head rotation or head shift parallel to the surface of the monitor. Furthermore, when the shaded shape was changed from a circle to a square, or the shading type was changed from gradual to stepwise, the difference in performance between vertical and horizontal shading disappeared in chimpanzees, but persisted in humans. These results suggest that chimpanzees process shading information in a different way from humans.

Key words Shape from shading Visual search Texture segregation Chimpanzees Humans 


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Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • Masaki Tomonaga
    • 1
  1. 1.Department of Behavioral and Brain Sciences, Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan e-mail:, Tel.: +81-568-630549, Fax: +81-568-622428JP

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