Dynamic properties of vision-III: twin flashes, single flashes and flickerfusion

The threshold of two identical rectangular incremental flashes or "twin flashes" was measured as a function of the interval between the flashes. The measurements were effected with a 1° foveal stimulus for various background intensities. The relationship with threshold characteristics for single flashes of variable duration, measured by the same subjects under identical conditions, is demonstrated. The characteristics accord with the theoretical values calculated on the basis of the theoretical model discussed in Part II, from the subjects' flicker-fusion curves determined under identical experimental conditions.