Fitts's Law
Fitts' Law
A predictive model of human movement primarily used in human–computer interaction and ergonomics (such as moving a mouse cursor on a screen). This scientific law predicts that the time required to rapidly move to a target area is a function of the ratio between the distance to the target and the width of the target.
Origin
American psychologist Paul Morris Fitts proposed the law in his 1954 paper quantifying target selection difficulty. Fitts studied airplane-cockpit design during World War II, arguing that losses attributed to human error often stemmed from poor design. Influenced by Shannon's information theory in the 1950s, Fitts sought the "bandwidth of human movement"—how many repetitive movements could occur per time interval. His model, now foundational in HCI and ergonomics, predicts that movement time depends on distance-to-width ratio.