On the Origin of the Ponzo Illusion: An Attentional Account.

The Ponzo illusion is a famous optical illusion that is not well understood so far. Here we suggest that its origin is closely linked to distribution of spatial attention. In essence, it arises because the size of the attentional field varies between different parts of the stimulus layout, which comes with different spatial resolution and, as a consequence, different apparent sizes of the objects in the stimulus display. We report four experiments (conducted in 2022 and 2023), which support this approach. The illusion substantially decreases when the stimulus layout is modified so that the size of the supposed attentional field is equalized for the crucial parts (Experiment 1). Moreover, we induce a Ponzo-like illusion by means of attentional cues only (Experiment 2). The perceived spatial frequency differs for different parts of the stimulus layout consistent with predicted changes in spatial resolution (Experiment 3). Attentional cuing exerts an analogous influence on the apparent spatial frequency (Experiment 4). The presented approach provides a novel look at the origin of the Ponzo illusion and related phenomena. Public Significance Statement: In this study, we introduce and test a novel explanation of the Ponzo illusion. We propose that this optical illusion is a byproduct of different spatial resolutions for different parts of the stimulus layout resulting from different attentional distributions. Four experiments are reported which provide support for this approach. The presented idea provides a novel look at the origin of optical illusions. [ABSTRACT FROM AUTHOR]