August 2016
Volume 16, Issue 12
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2016
Observers misperceive the size of artificial limbs
Author Affiliations
  • Ritika Mazumder
    Rhodes College
  • Jason Haberman
    Rhodes College
Journal of Vision September 2016, Vol.16, 1411. doi:10.1167/16.12.1411
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      Ritika Mazumder, Jason Haberman; Observers misperceive the size of artificial limbs. Journal of Vision 2016;16(12):1411. doi: 10.1167/16.12.1411.

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      © 2017 Association for Research in Vision and Ophthalmology.

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Abstract

In creating a prosthetic device for lower-limb amputees, prosthetists report purposely making the limb smaller along the width dimension than the corresponding intact limb. This is in response to the patients' report that the limb appears too 'bulky' if exactly matched in size to the intact limb. These experiments investigated the veracity of this perceptual bias. We first verified that prosthetists do, in fact, make prostheses smaller than the corresponding intact limb by comparing the size of both in a set of 35 images depicting patients wearing artificial limbs. The results revealed that prosthetists make the artificial limbs on average three percent smaller than the intact limb. Next, we explored whether observers exhibited a perceptual bias in perceiving prostheses viewed in the context of a body. Participants adjusted the width of the prosthesis in the same set of images (both upright and inverted) until it looked 'right.' Unexpectedly, observers adjusted the prosthetic limbs to be larger that the intact limbs by about seven percent, suggesting they perceived it to be smaller than the intact limb. Although the bias persisted when the images were inverted, it was significantly reduced, suggesting configural processing enhanced the size misperception. In a separate control experiment, when observers were instructed to adjust the size of the intact limb, the size bias was significantly mitigated. Further, when observers adjusted the prosthetic limb without the context of a body (i.e., only the prosthetic and intact limbs were visible), the size bias was again greatly reduced. Overall, the results suggest that observers underestimated the size of a prosthetic device, and this was most evident in the context of whole, upright bodies. However, the direction of this bias is unexpected given the clinical standard. It remains to be seen whether amputees exhibit a similar perceptual bias under formal testing conditions.

Meeting abstract presented at VSS 2016

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