Have you ever bought something online and way overestimated or underestimated its measurements? Even if the measurements are given, sometimes it’s still hard to visualize it and can be surprising when you finally see it in person. Did you know that we can’t accurately represent how long the back of our own hands are? According to a new study, we don’t know the back of our hands well at all.
This surprising study published in PLoS ONE this past March discovered that our views of the back of our own hands are astonishingly distorted—but not our palms. It seems contradictory that since we see the backs of our hands all the time, we should know them well, just like the saying goes; but our perception of them even changes whether they’re upright or sideways.
Forty healthy, adult participants were recruited for the study and two photos were taken of the back of their hands, except one photo was distorted. They then adjusted the distorted photo until the participants said they had reached the image of what their hands looked like in reality. Participants perceived the length of the back of their hand differently than the length of the palm of their hands by overestimating the length of the backs. The length of their palms, however, was perceived accurately.
The brain misrepresents the length of the back of the hands despite seeing the backs displayed most predominately and over a lifetime. The width of the back of the hands was also perceived inaccurately when it was held upright but was more accurately perceived when held sideways. None of these variations existed for the palm of the hand!
Deciphering how the brain registers, measures, and perceives the hands is important to understanding how to interpret the visual system of the brain and how to help those people who may have extremely inaccurate perceptions of their own body or body parts. There’s always more than meets the eye when it comes to how the brain interacts with its physical surroundings and body.
Sarah D’Amour, Laurence R. Harris. The perceived size of the implicit representation of the dorsum and palm of the hand. PLOS ONE, 2020; 15 (3): e0230624 DOI: 10.1371/journal.pone.0230624