Do Domestic Dogs (Canis lupus familiaris) Perceive Numerosity Illusions?
Laboratory of Applied Ethology, Department of Comparative Biomedicine and Food Science, University of Padua, Piazzetta del Donatore, 4, 35020 Legnaro, Italy
Department of General Psychology, University of Padua, 35131 Padua, Italy
Padua Neuroscience Center, University of Padua, 35131 Padua, Italy
Author to whom correspondence should be addressed.
Received: 15 October 2020
Revised: 18 November 2020
Accepted: 2 December 2020
Published: 4 December 2020
Studying visual illusions in animals allows researchers to reveal similarities and differences between how human and non-human species perceive the world around them. Recently, investigations into dogs have found evidence for the differential perception of visual illusions, when compared with human observers. Here, we extended this line of investigation by testing dogs’ susceptibility to numerosity illusions. This type of illusion occurs when an individual under- or overestimates the number of objects presented in a visual scene owing to the spatial arrangement of the objects. In the current study, we observed the spontaneous likelihood for dogs to approach a larger quantity of food items. In Experiment 1, we first established whether dogs would try to maximize their food intake within the experimental context. Following this, Experiments 2 and 3 presented food items arranged so as to generate a well-known numerosity illusion—the Solitaire illusion. Overall, dogs were able to select the larger quantity of food (Experiment 1), but did not exhibit any evidence of a numerosity misperception in Experiments 2 and 3. Our results reinforce the idea that dogs’ representation of the world differs significantly from ours.