Flicker sensation depends on the frequency of the interment light stimulus, but the frequency required for a given criterion of flicker sensation shows a marked variability different occasions with the same observer, or for different observers. This variability was studied using the multiple criterion technique, flicker judgments being obtained fro twenty subjects on a number of occasions. In one set of experiments the whole visual field was stimulated, in another field approximately 20 x 30. Four criteria of flicker sensation were employed including the customary criterion of "just perceptible" flicker. The results showed that: (a) Small changes in stimulus frequency cause large differences in the noticeably of flicker and in the sensation of discomfort caused by flicker. (b) Large changes in stimulus frequency cause little change in the apparent frequency of flicker, which remains constant around 16 c.p.s.. (c) As stated above, sensitivity varies markedly both between subjects and between occasions.
Abstract