Abstract
The proportion of light flashes detected by naive subjects was determined as a function of two flash groupings and two levels of flash intensity. One flash grouping, the “massed” condition, consisted of two groups of six flashes. The flashes were presented at the rate of one flash per second with about 1° of arc separations. The groups were separated by approximately 90 sec of time and 90° of arc. The second, or “distributed” condition, of twelve flashes presented at the rate of one flash for each 10° of arc and 10 sec of time. The illuminance level of these two conditions was equivalent to 0.13 kmc. One group of subjects was run under the “distributed” condition when the illuminance was increased to 0.935 kmc. There was no significant difference in the proportions of subject detecting flashes where flash distribution was the independent variable. A greater proportion of flashes was seen under the “distributed” condition than under the “massed” condition. More subjects made detections when the stimulus was 0.935 kmc than when it was 0.13 kmc.
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