Lateralized embodiment of ambiguous human silhouettes: Data on sex differences

Abstract

Whereas the role of observers' sex has already been addressed in research on embodied cognition, so far it has been neglected as regards laterality effects in embodied cognition. Here, we report further analyses of the data used in our paper “Hemispheric asymmetries in the processing of body sides: A study with ambiguous human silhouettes” [1], where participants had to indicate the perceived orientation of silhouettes with ambiguous front/back orientation and handedness presented in the right and left hemifield. Specifically, the variables examined in the associated paper (the number of right- and left-sided silhouettes perceived as front- and back-facing in each hemifield; the number of silhouettes perceived as right- and left-handed in each hemifield) are analyzed by also factoring in participant's sex). Moreover, data are provided and analyses are performed both for the total sample of participants and for the sample of right-handed participants only. For further details, as well as for the interpretation and discussion of the data, the reader is referred to the main article [1] and its Supplementary Material.

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]).…”

“…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.…”

“…To explain this lateralized facing effect, the authors proposed that the lateralized embodiment of an observed point-light walker is facilitated when the side of the visual cortex that processes the stimulus corresponds with the side of the sensory-motor cortices that process the hemibody seen in the foreground (for consistent findings with body part stimuli, see [22,23]). Moreover, we found that static human silhouettes with ambiguous handedness were interpreted more frequently as right-handed in the RVF than in the LVF [2,4]. Therefore, it is plausible that the hemifield of presentation promotes a laterally biased perception of ambiguous human bodies on the basis of the motor representations stored in the more stimulated (i.e., contralateral) hemisphere.…”

“…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].…”

Human Lateralization, Maternal Effects and Neurodevelopmental Disorders

“…On the other hand, right-handedness might also be fostered by children imitating adult’s manual preferences (Fagard and Lemoine, 2006 ). Similar mechanisms might be involved not only in the development of handedness, but also in the attentional bias toward the right side of others’ body observed in both right- and left-handers (Marzoli et al, 2015 , 2017a , b , 2019 ; Lucafò et al, 2016 , 2021 ; see also Marzoli et al, 2014 ), which in turn could account for the left-handers’ advantage in fighting and sports (e.g., Groothuis et al, 2013 ). Although the relative weight of genetic and environmental determinants of handedness has not been established yet, epigenetic effects have been hypothesized at both the molecular (Leach et al, 2014 ) and the behavioral level (Schmitz et al, 2017 ), and the same should be true for other instances of functional asymmetries.…”