Minding gaps on the skin: Opposite bisection biases on forehead and back of one’s head

Abstract

Humans perceive the world from an egocentric perspective, while being able to mentally take a third person's perspective. Graphesthesia tasks revealed that letters written on the back of one's own head are consistently perceived from an embodied perspective, while the perspective on one's front is less consistent and often disembodied. We developed a cutaneous gap bisection task as a more discrete measure of the perspective on the body. In analogy to a visual pseudoneglect, we expected bisections to deviate toward the left ear when perceived from an embodied perspective. While this hypothesis was confirmed for gap bisections on the back, the results on the front suggest overall a disembodied perspective. Contrary to our expectation, this pattern was not predicted by the spontaneous perspective participants took in a graphesthesia task, indicating different cognitive mechanisms. We discuss these findings in the frame of the current literature on spatial attention and perspective taking. AbstractHumans perceive the world from an egocentric perspective, while being able to mentally take a third person's perspective. Graphesthesia tasks revealed that letters written on the back of one's own head are consistently perceived from an embodied perspective, while the perspective on one's front is less consistent and often disembodied. We developed a cutaneous gap bisection task as a more discrete measure of the perspective on the body. In analogy to a visual pseudoneglect, we expected bisections to deviate towards the left ear when perceived from an embodied perspective. While this hypothesis was confirmed for gap bisections on the back, the results on the front suggest overall a disembodied perspective.Contrary to our expectation, this pattern was not predicted by the spontaneous perspective participants took in a graphesthesia task, indicating different cognitive mechanisms. We discuss these findings in the frame of the current literature on spatial attention and perspective taking.

Action body representations: more pronounced effect of hands than the whole body at a more explicit level of awareness

“…The stimuli selected to represent the motor imagery were influenced by visual and motor imagery literature (Isaac et al,1986). Stimuli were presented from the first-person perspective/egocentric perspective for the "self" condition or the third-person/allocentric perspective for the "other" condition (Frassinetti et al, 2011;Lenggenhager et al, 2016;Milner & Goodale,1995). The stimuli words from the concepts ("self" vs "other") were displayed embedded in a picture of the body district.…”

Emotional body representations: more pronounced effect of hands at a more explicit level of awareness

“…The target words and their respective categories were chosen based on previous studies which utilised the same paradigm to explore more implicit emotional body representations (Carey & Preston, 2019;Gumble & Carels, 2012;Preston & Ehrsson, 2018). Stimuli were presented from the first-person perspective/egocentric perspective for the "self" condition or the third-person/allocentric perspective for the "other" condition (Frassinetti et al, 2011;Milner & Goodale,1995;Lenggenhager et al, 2016). To prevent order effects, the IATs were completed in random order.…”

“…Indeed, virtual reality (VR) interventions are used to enhance the existing treatment protocols (Riva, 2004;Riva et al, 2002) for eating disorders mostly focus on the experience of the whole body or certain body districts such as the face, abdomen, buttocks and thighs derived from perceptual body image research (Keizer et al, 2016;Riva, 1998). However, there are distinct functional and sensory demands between our hands and feet (Flögel et al, 2016;Mancini et al, 2014) with differences in thermosensitivity (Ackerley et al, 2014), body representations between upper (e.g., face, hands) and lower body districts (e.g., legs and feet) (Caggiano & Cocchini, 2020;Mora et al, 2018;, as well as between front and back sides of the body (Lenggenhager et al, 2016). Hence, it is not clear whether we can generalise the results from the whole body to its different body districts.…”

Exploring ghost bodily sensations: differences across trait and state experiences

“…Hands are also twice as thermosensitive as the feet (Ackerley et al, 2014) and this relates to the greater cortical representation of hands compared to feet (Penfield & Rasmussen, 1950) or due to the thermoregulation of our body to maintain thermal homeostasis (Filingeri et al, 2018). In terms of our whole body, SPS might differ at this level due to differences in body representations between upper (e.g., face, hands) and lower body districts (e.g., legs and feet) (Caggiano & Cocchini, 2020;Mora et al, 2018;, as well as between front and back sides of the body (Lenggenhager et al, 2016). Therefore, there might be differences in the SPS experience (i.e.…”