engleski

The rotated snow tire traffic sign illusion

B45 traffic signs depict a chained tire signalling the need for suitable equipment in winter conditions on the road. The tire is vertically oriented within a blue circle. Previous research has shown that the circle is routinely perceived as being modestly distorted in a manner that visually „lengthens“ its horizontal compared to its vertical diameter. The goal of this study was to show that this illusion persists when stimuli are rotated by 90 degrees. The experiment was conducted using the method of constant stimuli in which participants had to choose whether stimuli were distorted in the horizontal or vertical dimension. All participants completed three different situations: a blank blue stimuli (control), a blue circle with a white ellipse inside, and the sign itself. Points of subjective equality (PSE) were calculated from the data. It was predicted that participants would perceive the sign as distorted in the vertical dimension because of the rotation and that the PSE would be significantly different when compared to control stimuli. Analyses of PSEs show that participants perceive the sign as significantly distorted in the vertical dimension when compared to control stimuli, with the ellipse falling in between the two. The illusion was persistent despite stimuli rotation. It is suggested assimilation processes may underline the illusion with an open discussion on whether there is a contribution of the fact that the tire is perceived as three dimensional. Overall the results are in line with previous research on standard, unrotated stimuli.

shape perception; shape distortion; traffic sign illusion

nije evidentirano