Detection of Changes in Spatial Position: IV. Multiple Display Fields, Display Aiding, and Interference

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Abstract
The detection of changes in spatial positon was examined for random-dot visual patterns for sequences of 2 to 16 successive display fields. The results show that operators integrate displacement information across successive display fields; detection is nearly invariant with a fixed total displacement over successive display fields, whether the status of a particular dot is queried or whether the observer must indicate only whether any dot in the field has been displaced. The critical variable is identified as the interval between successive display fields. Display aiding, represented by a trail of displacements, is extremely effective; strikingly large performance changes—from near chance to near perfect—are observed as a function of the length of the trail, especially at long intervals between successive displacements. The rate of trail fading proved to be a relatively insensitive variable. Three forms of visual interference were distinguished: clutter, or stationary noise; jitter, or stationary noise modified by a random walk; and random noise. Random noise was substantially more interfering than clutter. Implications for the design of displays are briefly discussed.