The effects of movement direction and hemispace on estimates of distance traveled

BACKGROUND/HYPOTHESIS: The degree of attention directed to a stimulus and the presence of anisometric representations can alter the perception of the magnitude of a stimulus. We wanted to learn if normal right-handed subjects' estimates of distance traveled are influenced by the right-left direction or hemispace of movements. METHODS: We had blindfolded participants estimate the distance their arm was moved in a rightward or leftward direction, in right and left hemispace. Since we wanted subjects to estimate the distance traveled rather than compute the distance between the start and finish points, the subjects' arms were passively moved in sinusoidal trajectories at a constant speed. RESULTS: Subjects estimated leftward movements as longer than rightward movements, but there was no effect of hemispace. COMMENTS/CONCLUSIONS: People often attend more to novel than routine conditions and therefore participants might have overestimated the distance associated with leftward versus rightward movement because right-handed people more frequently move their right hand in a rightward direction and learn to read and write using rightward movements. Thus, leftward movements might be more novel and more attended than rightward movements and this enhanced directional attention might have influenced estimates of magnitude (distance).