Using traditional horizontal-vertical illusion figures and single lines to directly compare haptics and vision

Abstract

The horizontal-vertical illusion (HVI) is the tendency for a vertical line to be perceived as longer than a horizontal line of the same length. The HVI is commonly reported and investigated as a visual phenomenon. It has, however been found to occur haptically. The comparatively small number of haptic HVI papers paired with varied stimuli and measures make it problematic to directly compare visual and haptic forms of the illusion. The current paper reports a study in which the visual and haptic HVIs were directly compared. Three sets of stimuli were used in an attempt to resolve previous limitations: L-figures, inverted Tfigures, and separated horizontal and vertical lines. These stimuli were presented in two lengths: 3 and 9 cm. The dependent variable was percentage error between the horizontal and vertical -no error represents an absence of illusion. As expected, inverted T-figures produced an illusion significantly stronger than both the L-figures and single lines, which did not differ from each other. Stimuli of 9 cm produced stronger illusions than those that measured 3 cm, and stimulus size interacted with modality. The consequences of these findings for earlier research are discussed and suggestions are offered as to what causes this and other illusions.

The intensity order illusion: temporal order of different vibrotactile intensity causes systematic localization errors

“…The rate of discovery of new tactile and haptic illusions has increased in recent years (Hayward 2008(Hayward , 2015Lederman and Jones 2011), and there are interesting parallels between perceptual effects across senses (Konkle et al 2009). Many well-known optical geometrical illusions have tactile counterparts such as the Delboeuf (Gentaz and Hatwell 2004), vertical-horizontal (Howell et al 2013), Bourdon (Day 1990), Ebbinghaus (Ziat et al 2014), Müller-Lyer (Millar and Al-Attar 2002), and Ponzo and Oppel-Kundt illusions (Suzuki and Arashida 1992). For tactile perception, there are characteristic spatiotemporal illusions related to underestimation of interstimulus distance and overestimation of interstimulus time (Goldreich 2007), such as the tau effect (Helson 1930;Lechelt and Borchert 1977), the kappa effect (Suto 1951), and the apparent haptic movement illusion (Carter et al 2008;Sherrick and Rogers 1966).…”