Left and Right Hands Rely on Different Senses

The "split-brain studies," done by Gazzaniga, Sperry, and others, long ago confirmed the lateralization of language and handedness. New research at the University of Michigan suggests that certain senses may be tied to handedness as well. In right-handed people, the dominant hand is more dependent on vision for guidance while the non-dominant (left) hand is more attuned to the sense of proprioception and touch from muscles, joints, and skin.

In the first task, which assessed visual control over movement, subjects were shown a lighted target to their left or right for less than a second. Then they were asked to mark the location the target had been in by moving a laser pointer attached to the lever system. The measurement was made with both hands, and with targets on the same side, or across from, each arm. Smaller errors were found for the preferred right arm in this visual task.

In the second task, the left or right forearm of blindfolded subjects was moved to a target position and held for three seconds before being returned to the start position. Then the subjects were told to return to that spot with either the same arm or the opposite arm. In this test, errors were smaller on the left, or non-preferred, side.

"We really saw marked differences in matching accuracy between arms, depending on what type of sensory input was used to present the target," Goble said.

Check out this movie of the experimental setup used in the study.