Length perception of horizontal and vertical bisected lines

Abstract

In an inverted T figure, the vertical line is largely overestimated (Avery and Day in J Exp Psychol 81:376-380, 1969). This vertical overestimation results from the vertical and bisection biases. Line orientation biases length perception in the sense that the vertical line of a L shape is perceived as longer than the horizontal line of the same physical length. In the inverted T figure, the vertical line is overestimated because of its orientation but also because the horizontal line is bisected. In the current study, we used various two-line configurations to investigate the role of bisection a/symmetry in line length perception and its interaction with the vertical bias. Experiment 1 showed that symmetry and asymmetry of bisection have different consequences on line length perception, as previously shown by Wolfe et al. (Percept Psychophys 67:967-979, 2005). Experiments 2 focused on the relation between the vertical and bisection biases by manipulating orthogonally line orientation and bisection a/symmetry. The results provided evidence that bisection can prevent the manifestation of the vertical bias, so that when the two lines are bisected, vertical lines are not anymore overestimated. These results are discussed in the light of recent findings claiming that saccades could play an essential role in length perception.

An investigation of the mechanisms underlying the effects of viewing distance and stimulus length on attentional asymmetries during line bisection

“…This overestimation is thought to arise from a vertical bias (in which the length of vertical lines is overestimated) and a bisection bias (in which bisected lines appear shorter) (Josev, Forte & Nicholls, 2011). The vertical bias is more relevant to the present study and results in an overestimation of length of 5% in vertical as compared to horizontal lines (Charras & Lupiáñez, 2010). Bearing this in mind, it is possible that participants perceived the vertical line to be slightly longer than the horizontal line.…”

Left of centre: asymmetries for the horizontal vertical line illusion

“…b or c) (Charras & Lupiáñez, 2010;Kunnapas, 1955;Wolfe, Maloney, & Tam, 2005). Charras and Lupiáñez (2010) have proposed that two mechanisms contribute to the HVI. The Wrst is a 'vertical bias' whereby vertical lines appear longer than horizontal lines of a similar length.…”

“…r) and minimised when the vertical line appears at either end of the horizontal line (i.e. b or c) (Charras & Lupiáñez, 2010;Kunnapas, 1955;Wolfe, Maloney, & Tam, 2005). Charras and Lupiáñez (2010) have proposed that two mechanisms contribute to the HVI.…”

“…In their Wrst experiment, Charras and Lupiáñez (2010) presented HVI stimuli where the vertical line was located at either end of the horizontal line (b or c), in the middle (r) and at two intermediate position to the left and right of centre. The HVI was strongest when the vertical line was in the centre, or at either end,-but was substantially reduced for the intermediate positions.…”

Titchener’s ⊥ in context 1—delimited, discrete monomotif patterns, line arrangements, and branching patterns

“…1 Yet, in vision, a minor effect of rotation sometimes remains (e.g., Charras & Lupiáñez, 2010;Mamassian & de Montalembert, 2010), which is bound to the presence of two lines in one's field of view, though: for 1 The notion of haptics is confronted here with touch: while the former mode of perception is based on the output of mechanoreceptors at the joints and muscles, the latter is based on the activity of receptive structures in the skin (Gardner & Johnson, 2013;Lederman & Klatzky, 2009). The ⊥ may also elicit a haptic-tactile illusion when a model or a raisedlines drawing is explored blindfoldedly by sliding one's finger tips across the figure (Day & Avery, 1970;Heller, Bracket, Salik, Scroggs, & Green, 2003), but that variant of the illusion is not dealt with here.…”