Abstract
The closer a line extends toward a surrounding frame, the longer it appears. This is known as a framing effect. Over 70 years ago, Teodor Künnapas demonstrated that the shape of the visual field itself can act as a frame to influence the perceived length of lines in the vertical-horizontal illusion. This illusion is typically created by having a vertical line rise from the center of a horizontal line of the same length creating an inverted T figure. We aimed to determine if the degree to which one fixates on a spatial location where the two lines bisect could influence the strength of the illusion, assuming that the framing effect would be stronger when the retinal image is more stable. We performed two experiments: the visual-field and vertical-horizontal illusion experiments. The visual-field experiment demonstrated that the participants could discriminate a target more easily when it was presented along the horizontal vs. vertical meridian, confirming a framing influence on visual perception. The vertical-horizontal illusion experiment determined the effects of orientation, size and eye gaze on the strength of the illusion. As predicted, the illusion was strongest when the stimulus was presented in either its standard inverted T orientation or when it was rotated 180° compared to other orientations, and in conditions in which the retinal image was more stable, as indexed by eye tracking. Taken together, we conclude that the results provide support for Teodor Künnapas’ explanation of the vertical-horizontal illusion.
Highlights
The vertical-horizontal illusion typically consists of a vertical line rising from the center of a horizontal line creating an inverted T figure (Figure 1)
The participants seemed to have more difficulty detecting targets when they were presented along the vertical meridian and when they were presented in the periphery
analysis of variance (ANOVA) revealed a main effect of Visual Field: F(2,31) = 6.48, p = 0.007 (Greenhouse-Geisser corrected)
Summary
The vertical-horizontal illusion typically consists of a vertical line rising from the center of a horizontal line creating an inverted T figure (Figure 1). Both lines are of equal length, the vertical line appears longer than the horizontal one. The most prominent theory to explain this illusion was proposed by Künnapas (1955) This theory, known as the framing theory, is based on the principle that the shape of the visual field is more elongated in the horizontal plane as a result. Eye Tracking and the Vertical-Horizontal Illusion of the combined visual fields from each eye merging together This shape of the visual field under binocular vision creates a framing effect whereby a vertical line appears longer than a horizontal line of the same length. This is because the former is closer to the boundaries of the visual field than the latter
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
