A Vast Right Arm Conspiracy? Handedness May Affect Body Perception

There are areas in the brain devoted to our arms, legs, and various parts of our bodies. The way these areas are distributed throughout the brain are known as “body maps,” and there are some significant differences in these maps between left- and right-handed people. For example, in left-handed people, there is an equal amount of brain area devoted to the left and right arms in both hemispheres. However, for right-handed people, there is more cortical area associated with the right arm than the left. Psychologists Sally A. Linkenauger, Jonathan Z. Bakdash, and Dennis R. Proffitt of the University of Virginia, along with Jessica K. Witt from Purdue University and Jeanine K. Stefanucci from The College of William and Mary, wanted to see if this difference in body maps leads to differences in how we perceive the length of our arms. For this study, volunteers were brought to the lab and estimated their perceived arm length and how far they could reach with their arms. As reported in Psychological Science, left-handed volunteers judged both of their arms to be the same length, but right-handed participants underestimated the length of their left arm — they consistently perceived their right arms as being longer. In addition, right-handed volunteers thought their right hands were larger than their left, when in fact they were both the same size. When guessing how far they could reach with their arms, left-handed volunteers estimated they could reach equally far with both arms, whereas right-handed volunteers predicted they could reach farther with their right arm. These findings suggest that body maps in our brain may really influence how we perceive our physical bodies.