Tactual-kinesthetic matching of horizontal extents by the long-term blind: Absence or reversal of normal left-side underestimation

Blind individuals show pseudoneglect in bisecting numerical intervals

“…We have previously demonstrated (Cattaneo et al, in press;Cattaneo et al, 2010) that congenitally blind individuals tend to err leftward when haptically bisecting physical rods (see also Bradshaw et al, 1986;Coudereau et al, 2006;Sampaio et al, 1995), thus exhibiting pseudoneglect (Jewell & McCourt, 2000). In sighted participants, the magnitude of the leftward bias in numerical bisection was found to correlate significantly with the magnitude of the leftward bias in physical line bisection (Longo & Lourenco, 2007).…”

“…pseudoneglect in this task does not depend on normal visual experience (Cattaneo et al, in press;Cattaneo, Fantino, Tinti, Silvanto, & Vecchi, 2010; for previous evidence, see Bradshaw, Nettleton, & Wilson, 1986;Coudereau, Gueguen, Pratte, & Sampaio, 2006;Sampaio, Gouarir, & Mvondo, 1995). However, whether blind individuals also show pseudoneglect in bisecting numerical intervals has not been investigated.…”

Spatial biases in peripersonal space in sighted and blind individuals revealed by a haptic line bisection paradigm.

“…In one condition, participants performed the task with their hands crossed. In this condition, the blind participants were found to err in protruding the rod leftward from the tube, whereas the sighted participants' bias was unaffected ( Bradshaw et al, 1986).The opposite directional bias in the crossed-hands condition (as compared with the uncrossed-hands condition) suggests that the blind participants tended to rely on body-centered coordinates more than the sighted controls. In particular, what was coded as left side of space by the blind participants depended on the position of their left hand, whereas sighted participants relied on eyecentered spatial codes, regardless of hand position ( Bradshaw et al, 1986).…”

“…Predictions for the vertical and radial planes were less straightforward. As mentioned earlier, individuals lacking any visual experience tend to rely mainly on body-centered or hand-centered coordinates (and less on objectcentered/allocentric codes) when representing the external space ( Bradshaw et al, 1986;Röder et al, 2004; for reviews, see Cattaneo et al, 2008;Thinus-Blanc & Gaunet, 1997). Accordingly, if the adoption of a body-centered reference frame (as compared with a more allocentric type of spatial representation) plays a major role in causing the unidirectional bias in haptic bisection of vertical and radial lines in the sighted, then blind participants should show a similar consistent downward/proximal bias ( Chewning et al, 1998;Shelton et al, 1990).…”

“…This has been explained in terms of kinestheticmotor mechanisms, which are inherent to haptic exploration and which are relatively body centered, thus inducing a toward-the-participant bias ( Chewning et al, 1998;Shelton et al, 1990). The haptic line bisection task has also been conducted with visually impaired individuals, offering an insight into hemispheric specialization in blind individuals ( Bradshaw, Nettleton, Nathan, & Wilson, 1986;Coudereau, Gueguen, Pratte & Sampaio, 2006;Sampaio, Gouarir, & Mvondo Mvondo, 1995). Studies using auditory localization paradigms suggest that the right hemisphere is specialized in spatial processing in blind individuals as well ( Gougoux, Zatorre, Lassonde, Voss, & Lepore, 2005;Voss et al, 2004;Weeks et al, 2000).…”