Fitts's Law

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Cole J: Fitt's Law

Jared: Fitts' Law (correct spelling = +bonus points)

Brad Twitty: Fitt's Law

Straight out of 1954 comes Paul Fitts and his undisputed law. The basic idea is that several factors are taken into account when judging the success rate of movement from a current position to some other desired position. Three main factors that are needed are the distance between start and end, the size of the target zone, and the time it takes to travel there. 

Fitts conducted his original experiments using an oscilloscope to have subjects write letters at various sizes and speeds. Using this gained knowledge, he expanded his series of tests to utilized a reciprocal tapping method. Subjects would use a stylus to tap alternately between two metal plates that would vary in size and distance. 

He then moved to using metal disk transfer. This was identical to the previous experiment, but did not allow for any errors to be made. His final experiment removed the disks and had subjects only transfer pins between a set of boards.

His results were the same across all experiments. To make things easier, you had to change one of three factors. Make the distance smaller, the target larger, or allow more time for the user.

I find that it is very interesting that Fitts's Law still holds after 55 years. The law itself has come to be the proving point for many tests, especially on modern user interfaces. One problem that many UIs suffer from is lots of small buttons being far away. If every designer would take a moment before they start to sit down and really understand Fitts's Law, then we would have fewer, slightly larger buttons closer to us, and hopefully a better UI. As long as no one goes overboard on the law by placing one single giant button in the middle of the screen. Sure it would maximize Fitts's Law, but what would it actually be good for?