Photic Driving of the Critical Flicker Frequency*

Abstract

A light pulsing above the critical flicker frequency (CFF) significantly elevates, and one pulsing below CFF significantly depresses, subsequent CFF measurements. The characteristics of these phenomena, their dependence upon the duration of fixation, the luminance of the measuring and the adaptation lights, and the duration of the after-effect are described in the present series of experiments. The effects are virtually as pronounced if the pulsing adaptation light is viewed with one eye and the measuring light with the other, as when both adapting and measuring lights are seen by the same eye. It is proposed that the driving is a direct consequence of a change in the frequency characteristics of the responses of cells in the visual system to photic stimulation. Measurements of the brightness of lights, pulsing at various rates immediately after viewing lights pulsing above and below the CFF, confirm certain predictions of this hypothesis.