Difference thresholds for intermittent photic stimuli as a function of rate of flash, number of flashes, and presentation time.

Abstract

Data were obtained on the difference threshold function for intermittent photic stimuli with the method of single stimuli. Combinations of rate of presentation (F), number of flashes in a train (N), and duration of a train (T) were selected to permit plotting difference thresholds as a function of all possible combinations of F, N, and T.The major findings of this study were as follows: (1)The number of flashes in a train has a negligible effect upon the difference threshold either in terms of ΔP or ΔF. Values of N ranged from 5 to 40 flashes.(2)The duration of a train has a negligible effect upon the difference threshold either in terms of ΔP or ΔF. Values of T ranged from 12 to 4 sec.(3)The difference threshold function for intermittent photic stimuli obtained with the method of single stimuli is comparable in form to the function obtained with the method of adjustment.(4)Expressing difference thresholds in terms of a period measure points up the similarity between the difference threshold functions obtained with intermittent photic and electric stimuli.