TOBIOJ The Open Biology Journal Open Bio. J. 1874-1967 Bentham Open TOBIOJ-2-137 10.2174/1874196700902010137 Biology Cognitive Understanding of Object Permanence in Mandrills (Mandrillus sphinx, L.) Gabel Anna Lucass Carsten M. Zimmer Stefanie Bietz Christina Schwenke Maren Wanker Ralf * Biozentrum Grindel, University of Hamburg, Martin-Luther-King Platz 3, 20146 Hamburg, Germany Address correspondence to this author at the Biozentrum Grindel, University of Hamburg, Martin-Luther-King Platz 3, 20146 Hamburg, Germany; E-mail: wanker@zoologie.uni-hamburg.de 20 11 2009 2009 2 137 140 01 01 2009 30 09 2009 06 10 2009 © 2009 Wanker et al. 2009 Ralf Wanker

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Object permanence tests are a standard procedure to test the cognitive ability to mentally follow a hidden object. To test this capacity in mandrills, we used visible and color-tracking with invisible displacement tests. During visible displacement the object was hidden and moved within its container in full view of the tested individual. During color-tracking with invisible displacement the object was hidden in a colored container, also in full view, but then moved within its container out of view. The tested mandrills were successful in the visible but not in the color-tracking with invisible displacement tests. They did not use the color as a cue for the correct container. One of the animals memorized the position of the container, in which the reward was dropped before the invisible displacement. We assume that the capacity of solving invisible displacement tests has evolved after the evolutionary separation of mandrills and apes.