Inversion Reveals Perceptual Asymmetries in the Configural Processing of Human Body

Abstract

Ambiguous human bodies performing unimanual/unipedal actions are perceived more frequently as right-handed/footed rather than left-handed/footed, which suggests a perceptual and attentional bias toward the right side of others’ body. A bias toward the right arm of human bodies could be adaptive in social life, most social interactions occurring with right-handed individuals, and the implicit knowledge that the dominant hand of humans is usually placed on their right side might also be included in body configural information. Given that inversion disrupts configural processing for human bodies, we investigated whether inversion reduces the bias toward the right side of human bodies. Consistent with our hypothesis, when presented with ambiguous stimuli depicting humans performing lateralized actions or movements, participants perceived a greater proportion of right-handed figures when the stimuli were shown upright than when the stimuli were shown inverted. The present findings seem to confirm our hypothesis that body configural information may include some form of knowledge about the probable handedness of other individuals, although alternative accounts involving the role of experience cannot be ruled out.

Hemifield-Specific Rotational Biases during the Observation of Ambiguous Human Silhouettes

“…Moreover, Burton et al [27] examined reaction times for CW and CCW mental rotations in the two hemifields, showing that CCW and CW rotations were more efficiently performed in the RVF and LVF, respectively. We point out that a hemifield-specific rotational bias could also account for previous findings with static human silhouettes [2][3][4]. Indeed, a perceptual bias for forward-facing motion exists [28,29] (see also [30]) that can also induce observers to interpret ambiguous figures consistently with a forward rather than backward motion [31][32][33] (see also [34]) and ambiguous human bodies as front-facing rather than back-facing [1][2][3][4]35,36] (for further instances of perceptual and attentional advantages for approaching rather than receding stimuli, see [37][38][39][40][41]).…”

“…We point out that a hemifield-specific rotational bias could also account for previous findings with static human silhouettes [2][3][4]. Indeed, a perceptual bias for forward-facing motion exists [28,29] (see also [30]) that can also induce observers to interpret ambiguous figures consistently with a forward rather than backward motion [31][32][33] (see also [34]) and ambiguous human bodies as front-facing rather than back-facing [1][2][3][4]35,36] (for further instances of perceptual and attentional advantages for approaching rather than receding stimuli, see [37][38][39][40][41]). Therefore, the combination of the bias to perceive forward-facing figures (which would be consistent with an inward rather than outward rotation) and the aforementioned hemifieldspecific rotational bias could increase the proportion of left-sided silhouettes (i.e., those in which the action is depicted-from the observer's point of view-on the figure's left side) and right-sided silhouettes (i.e., those in which the action is depicted on the figure's right side) interpreted as "potentially rotating" inward and CCW (and thus right-handed) in the RVF and as "potentially rotating" inward and CW (and thus left-handed) in the LVF.…”

“…The preference for perceiving right-limbed actions did not correlate with the degree of participants' handedness in previous studies with ambiguous human body stimuli [1][2][3][4][5]19,20], and thus it is plausible that such tasks involve relatively more visual than motor processes. Nonetheless, there is also some evidence for a role of motor representations, at least under certain conditions.…”

“…In recent studies [1][2][3][4], we found that when right-and left-handed subjects were required to indicate the orientation of ambiguous (in terms of front or back view) figures representing human silhouettes in the act of performing one-handed manual actions, both groups reported perceiving the figures more frequently as oriented consistently with a right-handed movement than with a left-handed movement. Similar findings were reported for dynamic stimuli representing ambiguous human bodies represented in the act of performing unimanual and unipedal movements [3,5,6].…”

“…In recent studies [1][2][3][4], we found that when right-and left-handed subjects were required to indicate the orientation of ambiguous (in terms of front or back view) figures representing human silhouettes in the act of performing one-handed manual actions, both groups reported perceiving the figures more frequently as oriented consistently with a right-handed movement than with a left-handed movement. Similar findings were reported for dynamic stimuli representing ambiguous human bodies represented in the act of performing unimanual and unipedal movements [3,5,6]. These results indicate an attentional/perceptual bias toward the right side of the human body and are also consistent with findings from research investigating the perception of sport actions, according to which the outcomes of right-limbed movements can be anticipated better than the outcomes of leftlimbed movements [7][8][9][10][11][12][13].…”