Arm's Length: A Relative Measure (image) Brown University Caption People judge depth most accurately at a distance that corresponds with their arm length (green triangle). Too close and they overestimate depth (yellow); too far leads and they underestimate (blue). If they perceive their arm to be longer, researchers found, the whole continuum shifts farther away. Credit Istituto Italiano di Tecnologia Usage Restrictions with credit Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.