A prediction model used in human-computer interaction. It states that the time required to move to a target area rapidly increases as the distance to the target increases. The law was proposed by Paul Fitts, an American psychologist, in 1954 as a mathematical model of movement with limited cognitive capacity.
Fitts hypothesized that one would quickly select its first apparent target when reaching for an object before considering alternatives — a phenomenon called "target fixation." This tendency would increase progressively with increased distance between the subject and object until it eventually became exponential (i.e., too far away).