The contribution of the shading pictorial cue on the tridimensionality perception in dogs

The perception of Two-dimensional images in dogs has been largely investigated; however, to date, there is very limited empirical evidence regarding their ability to perceive three-dimensionality through pictorial cues. The aim of the present study was to assess the contribution of the pictorial cue of shading on dogs' perception of three-dimensionality. To achieve this, twenty-four dogs were subjected to two conditions: a control condition, in which a three-dimensional stimulus (i.e., a ball) was shown rolling on a planar surface until it fell into a real hole, and a test condition, in which the same three-dimensional stimulus rolled on the planar surface until passing over an illusory hole (i.e., a two-dimensional pictorial representation of a real hole). The application of the violation-of-expectation paradigm did not reveal any significant difference in observation time between the two conditions, suggesting that the pictorial cue of shading in the two-dimensional image of the hole could not elicit the perception of three-dimensionality. However, a significant difference between the two trials was observed, with dogs showing greater attention during the first trial compared to the second.