Do Dogs See the Ponzo illusion?

Sarah-Elizabeth Byosiere,Philippe A Chouinard,Tiffani J Howell,Nicholas J Rutter Rutter,Lynna C Feng,Jessica K Woodhead

doi:10.26451/abc/.04.04.01.2017

Abstract

Do Dogs See the Ponzo illusion?

Highlights

While domestic dogs (Canis familiaris) play a large role in human daily lives, little is known about how they perceive the visual world
Assimilation theory has been proposed by Pressey (1971) to explain the Ponzo illusion based on two main postulates, which are as follows: (1) Whenever judgments are made of a series of magnitudes, the smaller magnitudes in that series will be overestimated and the larger magnitudes will be underestimated
While most dogs showed a slight susceptibility to the illusion, in that their score was above, rather than below, the chance level performance of 50% correct, there was insufficient evidence to suggest that any individual dog was susceptible to the illusion above chance levels at α = 0.05 (p ≥ 0.06 for all tests)

Summary

Introduction

While domestic dogs (Canis familiaris) play a large role in human daily lives, little is known about how they perceive the visual world. Recent research suggests that dogs may perceive certain visual illusions differently than humans. A one-sample t-test of the dogs’ responses to the Ponzo stimuli in Experiment 1 demonstrated illusion susceptibility at the group level; no individual dog performed significantly above chance in binomial tests. As most animals tested previously have demonstrated human-like susceptibility to the Ponzo illusion, these findings have implications for theoretical explanations. The divergence of results between dogs and humans/other animals suggest that mechanisms underlying perception of the Ponzo illusion may differ across species and that care should be taken when using visual paradigms to test dogs’ cognitive skills. One of the most widely studied visual illusions is the Ponzo illusion This illusion typically consists of two sized targets (e.g., circles or lines) that appear unequal when superimposed over converging lines (Figure 1). (1) Whenever judgments are made of a series of magnitudes, the smaller magnitudes in that series will be overestimated and the larger magnitudes will be underestimated. (2) Other things being equal, a context which falls within the attentive field will be more effective than a context outside that field (Pressey, 1971, p. 172)

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