Human subjects were asked to identify one of seven possible luminance levels under Ganzfeld conditions. The luminance range investigated was 0.5–500.0 ft 1m. Earlier findings on the subjective effects of a Ganzfeld on humans were verified. Subjects performed significantly better under non-adapted than under adapted conditions. Under both conditions subjects tended to perform better after pupillary diameter had been fixed. Errors never exceeded 1 log10 unit in magnitude.
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