Effect of biomechanical constraints in the hand laterality judgment task: where does it come from?

Abstract

Several studies have reported that, when subjects have to judge the laterality of rotated hand drawings, their judgment is automatically influenced by the biomechanical constraints of the upper limbs. The prominent account for this effect is that, in order to perform the task, subjects mentally rotate their upper limbs toward the position of the displayed stimulus in a way that is consistent with the biomechanical constraints underlying the actual movement. However, the effect of such biomechanical constraints was also found in the responses of motor-impaired individuals performing the hand laterality judgment (HLJ) task, which seems at odds with the “motor imagery” account for this effect. In this study, we further explored the source of the biomechanical constraint effect by assessing the ability of an individual (DC) with a congenital absence of upper limbs to judge the laterality of rotated hand or foot drawings. We found that DC was as accurate and fast as control participants in judging the laterality of both hand and foot drawings, without any disadvantage for hands when compared to feet. Furthermore, DC's response latencies (RLs) for hand drawings were influenced by the biomechanical constraints of hand movements in the same way as control participants' RLs. These results suggest that the effect of biomechanical constraints in the HLJ task is not strictly dependent on “motor imagery” and can arise from the visual processing of body parts being sensitive to such constraints.

Typical action perception and interpretation without motor simulation

“…Our findings thus considerably extend previous results obtained with IDs or congenital paralysis (19,(32)(33)(34)(35). It has been shown that individuals with congenital paralysis of facial muscles recognize facial expressions despite their inability to perform facial movements (32).…”

“…It has been shown that individuals with congenital paralysis of facial muscles recognize facial expressions despite their inability to perform facial movements (32). It also has been found that individuals with upper limb dysplasia are influenced by body biomechanical constraints when asked to judge the laterality of hand drawings (33)(34)(35). The present study goes well beyond the scope of this previous evidence by demonstrating that motor simulation contributes neither to the ease (speed) of action recognition nor to its robustness and does not contribute to the ability to anticipate others' movements perceptually, to predict the outcome of their actions, to read their mental states from their kinematics, or to memorize their body postures and movements.…”

The origin of the biomechanical bias in apparent body movement perception

“…In favor of the visual hypothesis, we (Vannuscorps & Caramazza, 2015) recently reported the case of one individual born with no upper limbs, P.M., whose response latency when asked to judge the laterality of a visually presented hand (Parsons, 1987) was influenced by the biomechanical complexity of the hand posture and position, as found for typically developed individuals. For instance, P.M. was slower at recognizing a right hand pointing to the right side of the screen than the same hand pointing to the left side, reflecting the smaller degree of freedom associated with lateral than medial hand movements.…”

“…However, the nature of the representations and processes underlying this perceptual bias remains unclear. According to a "visual hypothesis", the biomechanical bias in action perception reflects implicit knowledge ("internal model") of the body movement capabilities, accumulated in the course of perceptual learning and encoded in the visual system (Marr and Vaina, 1982;Tessari, Ottoboni, Symes, & Cubelli, 2010;Vannuscorps, Pillon, & Andres, 2012;Vannuscorps & Caramazza, 2015). According to a "motor hypothesis", this perceptual bias relies on the observer's own body somatosensory and motor representations, learned through movement execution (Knoblich, 2008;Thornton, Pinto & Shiffrar, 1998;Stevens et al, 2000).…”

Typical predictive eye movements during action observation without effector-specific motor simulation

“…Participant D.C. is a 53-year-old man whose performance in various experiments has already been reported (Vannuscorps, Pillon & Andres, 2012;Vannuscorps, Andres & Pillon, 2013, 2014. He has a master's degree in psychopedagogy.…”