The contribution of linear perspective cues and texture gradients in the perceptual rescaling of stimuli inside a Ponzo illusion corridor

Abstract

We examined the influence of linear perspective cues and texture gradients in the perceptual rescaling of stimuli over a highly-salient Ponzo illusion of a corridor. We performed two experiments using the Method of Constant Stimuli where participants judged the size of one of two rings. In experiment 1, one ring was presented in the upper visual-field at the end of the corridor and the other in the lower visual-field at the front of the corridor. The perceived size of the top and bottom rings changed as a function of the availability of linear perspective and textures. In experiment 2, only one ring was presented either at the top or the bottom of the image. The perceived size of the top but not the bottom ring changed as a function of the availability of linear perspective and textures. In both experiments, the effects of the cues were additive. Perceptual rescaling was also stronger for the top compared to the bottom ring. Additional eye-tracking revealed that participants tended to gaze more in the upper than the lower visual-field. These findings indicate that top-down mechanisms provide an important contribution to the Ponzo illusion. Nonetheless, additional maximum likelihood estimation analyses revealed that linear perspective fulfilled a greater contribution in experiment 2, which is suggestive of a bottom-up mechanism. We conclude that both top-down and bottom-up mechanisms play important roles. However, the former seems to fulfil a more prominent role when both stimuli are presented in the image.

Individual differences in the Müller-Lyer and Ponzo illusions are stable across different contexts

“…The illusion magnitudes of the PZ down variants only resulted in very tiny-almost null-effects, while we expected these variants to be underestimated. Similar results were observed by Yildiz, Sperandio, Kettle, and Chouinard (2019) , who tested the effect of linear perspective cues and texture gradients on a Ponzo illusion. A significant perceptual effect was observed in the expected directions when both top and bottom elements of the illusion were presented.…”

When illusions merge

“…Here, we observed asymmetrical illusion magnitudes across both configurations of the same illusion. For example, the inward ML condition yielded stronger illusion magnitudes compared to the outward ML condition in absolute values (Figure 4; see also Cretenoud et al, 2020;Yildiz, Sperandio, Kettle, & Chouinard, 2019). In addition, some illusions showed very weak correlations between the two configurations.…”

Illusion susceptibility in domestic dogs

“…However, it is possible that dogs may demonstrate susceptibility to the Ponzo illusion when stimuli are further enhanced with additional linear perspective cues. Future research could present the Ponzo illusion embedded within pictorial stimuli as has been done with horses (Timney & Keil, 1996) and rhesus macaques (Fujita, 1996), as the addition of pictorial cues has been found to strengthen the illusion in humans (Fujita, 1996; Yildiz, Sperandio, Kettle, & Chouinard, 2019).…”