5.2.2 Flicker Flicker is another possible variable, but there is surprisingly little relevant research. Like motion, flicker also has two subvariables, frequency and phase. Flicker frequency, the speed of the on-off cycles, is selective by common fate, can be readily ordered, and could be promoted to quantitative by rescaling. There are, however, some problems with flicker frequency. First, it has very short length.
Phase refers to the relative point in the on-off duty cycle.
Marks of different phase are readily selective by common fate. However, phase is not readily ordered. Neither flicker frequency nor phase is likely associative. A third new variable is binocular disparity, which can be created by giving the left and right eyes slightly different views of the same visualization. In normal viewing disparity is not an important cue for judging distance.