The absolute velocity thresholds of movement were determined at 48 positions in peripheral vision. An aircraft-type instrument, with a standard altimeter hand, was located at random positions on the concave, black surface of an 80-in. Fiberglas hemisphere. Four types of movement were investigated (clockwise and counter-clockwise rotation, vertical and horizontal motion) under conditions of constant photopic lighting. While the subject fixated on the center point of the hemisphere, the absolute velocity threshold of each type of movement was determined for each position using the method of limits. Ten airline pilots served as subjects. The absolute threshold isograms on perimetric charts for both rotary and linear motion are elliptical in shape, with the horizontal axis approximately twice as long as the vertical axis. There is no difference between a subject’s ability to see clockwise or counter-clockwise rotation. An individual’s ability to perceive vertical motion is slightly better than his ability to perceive horizontal motion in the area adjacent to the horizontal axis. Velocity and area swept by the instrument hand are significant factors in the perception of movement, but they are not similarly correlated for all types of movement.
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