The Spatial and Temporal Parameters of Velocity Discrimination
Annual rept. 1 Apr-30 Sep 84
SMITH-KETTLEWELL INST OF VISUAL SCIENCES SAN FRANCISCO CA
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The target duration required for the precise discrimination of velocity is quite short, amounting to about 100 msec for a single moving dot or line target. While stroboscopic motion is an adequate substitute for continuous motion in velocity discrimination, optimal discrimination depends on the use of a strobe rate greater than 10 Hz. Generally human observers have difficulty detecting acceleration in moving targets. Over small distances 0.5-1 deg, timing signals from adjacent targets presented in a sequence are pooled, so that information about their relative onset time is lost. For example, given three adjacent lines, separated spatially by 0.1 deg and presented in a sequence apparent motion observers are unable to discriminate between a sequence in which a 10 msec interval separates the second from the reverse order 30 msec followed by 10 msec. Velocity discrimination is not affected by blur. Sinusoidal grating targets of 3 cyldeg or lower produce excellent discrimination. Sinusoidal gratings above 3 cycles per degree in spatial frequency are not adequate for fast velocities 1 degsec. Keywords Motion human performance Velocity discrimination Acceleration detection vision.
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