Truth is in the eye of the beholder: Perception of the Müller-Lyer illusion in dogs

Keep, Benjamin, Zulch, Helen and Wilkinson, Anna (2018) Truth is in the eye of the beholder: Perception of the Müller-Lyer illusion in dogs. Learning & Behavior . ISSN 1543-4494

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Truth is in the eye of the beholder: Perception of the Müller-Lyer illusion in dogs
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Visual illusions are objects that are made up of elements that are arranged in such a way as to result in erroneous perception of the objects’ physical properties. Visual illusions are used to study visual perception in humans and nonhuman animals, since they provide insight into the psychological and cognitive processes underlying the perceptual system. In a set of three experiments, we examined whether dogs were able to learn a relational discrimination and to perceive the Müller-Lyer illusion. In Experiment 1, dogs were trained to discriminate line lengths using a two-alternative forced choice procedure on a touchscreen. Upon learning the discrimination, dogs’ generalization to novel exemplars and the threshold of their abilities were tested. In the second experiment, dogs were presented with the Müller-Lyer illusion as test trials, alongside additional test trials that controlled for overall stimulus size. Dogs appeared to perceive the illusion; however, control trials revealed that they were using global size to solve the task. Experiment 3 presented modified stimuli that have been known to enhance perception of the illusion in other species. However, the dogs’ performance remained the same. These findings reveal evidence of relational learning in dogs. However, their failure to perceive the illusion emphasizes the importance of using a full array of control trials when examining these paradigms, and it suggests that visual acuity may play a crucial role in this perceptual phenomenon.

Additional Information:© The Author(s) 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Keywords:Dog, Canine, Cognition, Perception, Visual discrimination, Visual Illusion
Subjects:C Biological Sciences > C120 Behavioural Biology
Divisions:College of Science > School of Life Sciences
ID Code:33256
Deposited On:25 Oct 2018 15:12

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