Cross-cultural effects on the assumed light source direction: Evidence from English and Hebrew readers

Abstract

When judging the 3D shape of a shaded image, observers generally assume that the light source is placed above and to the left. This leftward bias has been attributed to experiential factors shaped by the observers' handedness or hemispheric dominance. Others have found that experiential factors can rapidly modify the direction of the assumed light source, suggesting a role for learning in shaping perceptual expectations. In the current study, instead, we assessed the contribution of cultural factors affecting the way visual scenes are customarily inspected, in determining the assumed light source direction. Left- and right-handed first language English and Hebrew participants, who read and write from left to right and from right to left, respectively, judged the relative depth of the central hexagon surrounded by six shaded hexagons. We found a left bias in first language English participants, but a significantly smaller one in Hebrew participants. In neither group was the light direction affected by participants' handedness. We conclude that the bias in the assumed light source direction is affected by cultural factors, likely related to the habitual scanning direction employed by participants when reading and writing their first language script.

Anticlockwise or clockwise? A dynamic Perception-Action-Laterality model for directionality bias in visuospatial functioning

“…As they claimed, both left- and right-handed observers show this tendency, but it is more pronounced among the right-handers. However, in agreement with subsequent studies (Mamassian & Goutcher, 2001; McManus, Buckman, & Woolley, 2004), a recent study failed to associate this orientation effect with handedness; instead, it demonstrated that cultural factors, such as scanning habits, can affect the way visual scenes are inspected and organized in determining the assumed light source direction (Andrews, Aisenberg, d’Avossa, & Sapir, 2013). Perhaps, as Proulx (2014) has precisely suggested, the perception of shape from shading may not be always necessarily based on a hard-wired internal representation of lighting direction; rather, it assesses the direction of lighting in the scene adaptively.…”

“…As discussed earlier in this review, some studies showed that the degree of preference for a top-left lighting condition in a 3D shape perception can be determined by handedness (Sun & Perona, 1998) whereas other studies claimed that this can be determined by cultural factors (e.g., reading direction), rather than handedness (Andrews et al, 2013). Ocklenburg and Güntürkün, 2009) demonstrated that the direction of head-turning in human adults can be associated with handedness or footedness (e.g., Ocklenburg & Güntürkün, 2009) whereas Shaki (2013) found that this can be shaped by cultural spatial habits, such as reading direction.…”

The light-from-above prior is intact in autistic children

“…We used a task that had previously shown subtle differences between groups whose long-term (cultural) experience of reading direction differed (Andrews et al, 2012), suggesting that it should have been possible to detect differences based on long-term experience between our groups if they were in fact present.…”

“…Following Andrews et al (2012), the relation between the proportion of convex judgments (“no” judgments in our game) and stimulus orientation was estimated for each participant using a multivariate logistic regression:$p(C|\theta )=1/(1+e^{-f(\theta )}])\text{,}$where for a given stimulus direction θ , f ( θ ) was a series of sine and cosine functions,$f(\theta )={\alpha }_0+{\alpha }_1\cos \theta +{\beta }_1\sin \theta \text{.}$…”

Lighting direction and visual field modulate perceived intensity of illumination

“…When interpreting the shape of ambiguous 3D surfaces the visual system exhibits a bias that directional illumination is mostly from above (Ramachandran, 1988; Sun and Perona, 1996a,b, 1998; Mamassian and Goutcher, 2001; Stone et al, 2009; de Montalembert et al, 2010; Morgenstern et al, 2011; Schofield et al, 2011; Andrews et al, 2013) and slightly from the left (Sun and Perona, 1998; Mamassian and Goutcher, 2001; Mamassian et al, 2003; McManus et al, 2004; Thomas et al, 2008; de Montalembert et al, 2010; Andrews et al, 2013). The light-from-above bias is well illustrated by experiments demonstrating that discs with top-dark luminance gradients are seen as concavities while those with top-bright luminance gradients are perceived as convexities (Ramachandran, 1988).…”