Abstract
In a study concerning visual body part recognition, a “self-advantage” effect, whereby self-related body stimuli are processed faster and more accurately than other-related body stimuli, was revealed, and the emergence of this effect is assumed to be tightly linked to implicit motor simulation, which is activated when performing a hand laterality judgment task in which hand ownership is not explicitly required. Here, we ran two visual hand recognition tasks, namely, a hand laterality judgment task and a self-other discrimination task, to investigate (i) whether the self-advantage emerged even if implicit motor imagery was assumed to be working less efficiently and (ii) how individual traits [such as autistic traits and the extent of positive self-body image, as assessed via the Autism Spectrum Quotient (AQ) and the Body Appreciation Scale-2 (BAS-2), respectively] modulate performance in these hand recognition tasks. Participants were presented with hand images in two orientations [i.e., upright (egocentric) and upside-down (allocentric)] and asked to judge whether it was a left or right hand (an implicit hand laterality judgment task). They were also asked to determine whether it was their own, or another person’s hand (an explicit self-other discrimination task). Data collected from men and women were analyzed separately. The self-advantage effect in the hand laterality judgment task was not revealed, suggesting that only two orientation conditions are not enough to trigger this motor simulation. Furthermore, the men’s group showed a significant positive correlation between AQ scores and reaction times (RTs) in the laterality judgment task, while the women’s group showed a significant negative correlation between AQ scores and differences in RTs and a significant positive correlation between BAS-2 scores and dprime in the self-other discrimination task. These results suggest that men and women differentially adopt specific strategies and/or execution processes for implicit and explicit hand recognition tasks.
Highlights
Over time, hands have developed in a remarkably humanspecific manner and serve as an important interface between human’s external worlds and their individual selves
Some studies did not reveal the effect of biomechanical constraints on the Reaction times (RTs) (e.g., Lust et al, 2006; Steenbergen et al, 2007). ter Horst et al (2010) suggested that engagement in motor imagery when performing a hand laterality judgment task depends on the used number of axes of rotation of the stimulus set
The present study investigated how the individual traits of typically developing (TD) university students modulated their performance in hand laterality judgment and self-other discrimination tasks using the Autism Spectrum Quotient (AQ) test (Baron-Cohen et al, 2001; Japanese version: Wakabayashi et al, 2004) and the Body Appreciation Scale-2 (BAS-2; Tylka and Wood-Barcalow, 2015; Japanese version: Namatame et al, 2017)
Summary
Hands have developed in a remarkably humanspecific manner and serve as an important interface between human’s external worlds (including other people) and their individual selves. The biomechanical effect is stronger when the hands were presented from palm than from back, because physically rotating palms is assumed to be more difficult than rotating backs of hands (Sekiyama, 1982; Parsons, 1987, 1994; Gentilucci et al, 1998; ter Horst et al, 2010; Bläsing et al, 2013; Zapparoli et al, 2014; Conson et al, 2020) These results indicate that hand laterality judgment tasks involve implicit motor imagery processes. Some studies did not reveal the effect of biomechanical constraints on the RTs (e.g., Lust et al, 2006; Steenbergen et al, 2007). ter Horst et al (2010) suggested that engagement in motor imagery when performing a hand laterality judgment task depends on the used number of axes of rotation of the stimulus set
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