Apparent brightness of a rotating arc-line as a function of speed of rotation

52 Ss were required to adjust the brightness of a center fixation line to equal that of the apparent brightness of an arc line viewed at a distance from the fixation point subtending an angle of 12° to the eye. Adjustments were made when the arc-line was stationary and rotating at speeds of 30, 45, 60 and 75 rpm. It was found that brightness enhancement occurred with increase in speed. This result was interpreted as supporting Ansbacher's account of distortion in the perception of moving arc-lines.