Exploring the Effects of Visual Frame and Matching Direction on the Vertical-Horizontal Illusion

Abstract

The work presented here uses an adjustment method to test the vertical-horizontal illusion across four different configurations: a cross-shape, an L-shape, an inverted-T and a rotated-T. We examine the modulatory role of the variables visual frame and direction of the adjustment on the illusory effect. Two experiments were performed, one with rectangular and one with curvilinear visual frames. Our data show that in both experiments, the size of the expected illusion increases from the cross-shape to the L-shape and from the L-shape to the inverted-T, where it reaches its maximum. In the rotated-T, the illusion reverses reaching a significant effect in the opposite direction. This pattern of results appears consistently across different experimental conditions, although the variability in the amount of illusory effect seems to be modulated by the intervention of the two variables examined. A dissection of the vertical-horizontal illusion has been carried out in terms of a two-factor explanation - anisotropy and bisection - interacting in different ways across configurations.

Is the Vertical-Horizontal Illusion a Byproduct of the Environmental Vertical Illusion?

“…Vertical-horizontal illusion task. Participants were instructed to draw a horizontal line below a 9.1 cm vertical line (as per Gavilán et al, 2017). The questionnaire item stated, "Please draw a horizontal line (--) as long as needed until your horizontal line is as long as the vertical line above.…”

“…The vertical-horizontal illusion can be measured through a basic task which involves estimating the length of a vertical line on a piece of paper by drawing a horizontal line of the same length on the piece of paper, typically in an upside-down T-shape. More often than not, people draw a horizontal line that is longer than the vertical line on the paper (Gavilán et al, 2017). Jackson and Cormack (2007) proposed that the verticalhorizontal illusion might be a byproduct of the mechanisms that generate the environmental vertical illusion.…”

Perception of length and orientation in dry immersion

“…The measurements in two groups were performed on the sensor monitors of different sizes. Though the rectangular frame size doesn’t influence the estimation of length ( Gavilán et al, 2017 ) and orientation ( Zoccolotti et al, 1992 ), and sex difference in the perception of orientation ( Brabyn and McGuinness, 1979 ) and inverted-T illusion ( Brosvic et al, 2002 ) are absent, we limited our interest by the potential dynamics of DI influence onto the parameters studied. As it can be seen from the presented results, the observed changes occurred at the beginning of the study, in relation to the first measurements.…”