I found it by the Google machine. According to Wikipedia:
In psychophysics, Korte’s law, also known more completely as Korte’s third law of apparent motion, is an observation relating the phenomenon of apparent motion to the distance and duration between two successively presented stimuli. It was originally proposed in 1915 by Adolf Korte. A modern formulation of the law is that the greater the length of a path between two successively presented stimuli, the greater the stimulus onset asynchrony (SOA) must be for an observer to perceive the two stimuli as a single mobile object. Typically, the relationship between distance and minimal SOA is linear.
Arguably, Korte’s law is counterintuitive. One might expect that successive stimuli are less likely to be perceived as a single object as both distance and SOA increase, and therefore, a negative relationship should be observed instead. In fact, such a negative relationship can be observed as well as Korte’s law. Which relationship holds depends on speed.
So, there you go. Anyone who can explain that to us is welcome to try.