Citation

Gulan T, Valerjev P, Dujmović M. Psych. J. 2018; 7(2): 68-76.

Affiliation

Deparment of Psychology, University of Zadar, Zadar, Croatia.

Copyright

(Copyright © 2018, Institute of Psychology, Chinese Academy of Sciences, Publisher John Wiley and Sons)

DOI

10.1002/pchj.208

PMID

29431259

Abstract

While observing a specific traffic sign in the field, we noticed an apparent distortion of size and shape of the circle that contained the sign. This novel illusion manifests as a distortion of the horizontal compared to the vertical dimension of the sign. The illusion seems to be underlined by similar mechanisms to those in the Delboeuf illusion. The aim of our study was to determine the existence and magnitude of the snow tire illusion. We conducted two experiments using the method of constant stimuli. The first experiment was conducted on the standard sign, while in the second, the stimuli were rotated 90° counterclockwise. Both experiments consisted of three conditions: the snow tire, the ellipse, and the simple circle (control) conditions. The data showed a robust illusion effect for both the standard and rotated sign compared to the control condition, with a large majority of participants experiencing the illusion. The snow tire illusion seems to be a combination of assimilation mechanisms of different magnitudes. The assimilation is larger for one dimension of the sign, thus producing the shape distortion. The illusion may be a manifestation of a thus far undocumented non-uniform effect of assimilation on perceived size and shape.

© 2018 The Institute of Psychology, Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

Language: en

Keywords

Delboeuf illusion; assimilation; shape distortion; traffic sign illusion