Differential effects of minified and magnified mirror visual feedback on the underlying misperception of hand size

A Treshi-Marie Perera,Poo Shin Mu,Jiun Ting Tan,Roger Newport

doi:10.3758/s13414-021-02262-9

A Treshi-Marie Perera, Poo Shin Mu + Show 2 more

Open Access

https://doi.org/10.3758/s13414-021-02262-9

Copy DOI

Abstract

Perception of the size of body parts, for instance the hand, has been shown to be distorted in healthy participants, with over- and underestimations of width and length, respectively. Illusory manipulations of body shape and size have highlighted the flexibility of the body representation and have also been found to update immediate perceptions of body size and surrounding objects. Here, we examined whether underlying misperceptions of hand width and length can be modified through exposure to illusory changes in hand size using a mirror visual feedback (MVF) paradigm. While questionnaire responses indicated subjective susceptibility to both magnified and minified manipulations, objective hand size estimates only showed significant differences following exposure to minifying mirrors. These variations might reflect differences in the way that stored representations are accessed or updated in response to size manipulations. Secondly, the findings further reinforce differences between subjective and objective outcomes of illusions on subsequent body perception.

Highlights

While it may seem intuitive that our somatic perceptions are hard-wired and resistant to manipulations, this is not always the case
Longo and Haggard (2010) identified systematic positional errors when healthy participants were asked to locate the position of a series of landmarks on the dorsum of the hand. The nature of these was such that hand width is overestimated while hand length is underestimated, with the extent of underestimations increasing from the thumb to the little finger (Longo & Haggard, 2010)
Percent underestimation of veridical hand length was 19.71%, while hand width demonstrated an overestimation of 28.21%

Summary

Introduction

While it may seem intuitive that our somatic perceptions are hard-wired and resistant to manipulations, this is not always the case. Longo and Haggard (2010) identified systematic positional errors when healthy participants were asked to locate the position of a series of landmarks (fingertips and knuckles) on the dorsum of the hand. The nature of these was such that hand width is overestimated while hand length is underestimated, with the extent of underestimations increasing from the thumb to the little finger (Longo & Haggard, 2010). This, together with the shape and organisation of the receptive fields of neurons representing the hand in S1, is thought to be linked to misperceptions of the metric properties of the body (or in this case, the hand; Longo, 2015; Longo & Haggard, 2010)

Methods

Results

Conclusion