Visual illusions provide a unique perspective into the role of the brain in the perceptual organization of visual stimuli, especially since the susceptibility to illusions varies between children, individuals with autism, and individuals from remote cultures. The mechanisms underlying these misperceptions are widely debated, but thought to be related to assimilation versus contrast effects, local versus global processing, or learned interpretations of perspective. Various animal species have also been found to be differently susceptible to visual illusions and have subsequently been investigated as models for understanding the differences in humans. In this study, we present dogs as a model for investigating differences in susceptibility to visual illusions within a single species. The extensive selective breeding of dogs from sight hounds bred for their visual abilities, to scent hounds bred for their olfactory abilities, to breeds bred for their visual appeal, has resulted in a wide range in behaviours and morphologies. It is reasonable to suggest that these behavioural and physical differences impact the dogs’ visual perceptions. For example, brachycephalic dogs have been shown to have a different distribution of ganglion cell density and more pronounced area centralis (McGreevy, Grassi, & Harman 2004), suggesting that they might perceive the world differently than dogs with longer noses. As such, dogs present a unique opportunity due to the vast within-species variation across breeds. This preliminary study looks at susceptibility of dogs to four common size-related visual illusions: the Ebbinghaus-Titchener (or Ebbinghaus) illusion, the Delboeuf illusion, the Müller-Lyer illusion, and the Ponzo illusion. The results will be presented and a plan for extending upon this preliminary study proposed.