Experimental evidence suggests that people underestimate relative depth for distractors beyond the fixate () and overestimate closeness (or ) for distractors nearer than the fixate. The motion/pursuit ratio has this relationship to the motion/pursuit depth formula, so it is possible that the ratio alone is a better estimate of the perceived depth.
The dark gray graph on the left is and the transparent colored graph is . On the right, the light gray graph is the relative depth ; the colored graphs are and at the critical time where these quantities peak. For more on peak times see "Motion/Pursuit Law in 2D (Visual Depth Perception 3)" in Related Links.