ORIGINAL PAPER Picture–object recognition in the tortoise Chelonoidis carbonaria Anna Wilkinson • Julia Mueller-Paul • Ludwig Huber Received: 23 January 2012 / Revised: 7 August 2012 / Accepted: 21 August 2012 / Published online: 4 September 2012 Ó Springer-Verlag 2012 Abstract To recognize that a picture is a representation of a real-life object is a cognitively demanding task. It requires an organism to mentally represent the concrete object (the picture) and abstract its relation to the item that it represents. This form of representational insight has been shown in a small number of mammal and bird species. However, it has not previously been studied in reptiles. This study examined picture–object recognition in the red- footed tortoise (Chelonoidis carbonaria). In Experiment 1, five red-footed tortoises were trained to distinguish between food and non-food objects using a two-alternative forced choice procedure. After reaching criterion, they were presented with test trials in which the real objects were replaced with color photographs of those objects. There was no difference in performance between training and test trials, suggesting that the tortoises did see some correspondence between the real object and its photo- graphic representation. Experiment 2 examined the nature of this correspondence by presenting the tortoises with a choice between the real food object and a photograph of it. The findings revealed that the tortoises confused the pho- tograph with the real-life object. This suggests that they process real items and photographic representations of these items in the same way and, in this context, do not exhibit representational insight. Keywords Picture–object recognition Á Tortoise Á Turtle Á Reptile Á Visual perception Introduction Recognizing that a picture represents an object is an easy, automatic process for humans living in a Westernized society. However, recent research has revealed that this is not necessarily the case for non-human animals or even for all humans (see Bovet and Vauclair 2000 for a review). To truly understand the nature of a picture, it is necessary to appreciate that the picture itself is an object that represents another object and to recognize what that other object is (DeLoache 2004). However, understanding that pictures are referential stimuli is not essential for discriminating between two pictorial stimuli. Fagot et al. (2000) proposed three possible modes of picture perception in animals: independence, confusion, and equivalence. In indepen- dence processing, an animal fails to relate the picture to real life in any way. It is possible to learn to discriminate pictures by processing them as combinations of features and/or patterns without any recognition of what the picture might represent. The confusion mode of processing refers to the animal perceiving the picture as the real object. It would therefore process the two stimulus types in exactly the same way. The third mode of processing, equivalence, refers to the ability to perceive that the picture is a repre- sentation of the object, but is not the object itself. Evidence of the confusion mode of processing by baboons and gorillas was presented by Parron et al. (2008). In a two-alternative forced choice procedure, baboons, A. Wilkinson (&) School of Life Sciences, University of Lincoln, Riseholme Park, Lincoln LN2 2LG, UK e-mail: awilkinson@lincoln.ac.uk A. Wilkinson Á J. Mueller-Paul Á L. Huber Department of Cognitive Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria L. Huber Messerli Research Institute, University of Veterinary Medicine Vienna, Medical University Vienna, and University of Vienna, Veterina ¨rplatz 1, 1210 Vienna, Austria 123 Anim Cogn (2013) 16:99–107 DOI 10.1007/s10071-012-0555-1