With all that said, it’s rare to see a UX practitioner use this formula in its raw form since there are simpler applications that stem from this formula. How should the 3-D amplitude be measured for the formula? The important points to consider are that time (T) is a function of distance (D) and width (W) and that the relationship is logarithmic. Fitts’s law is basically an equation that models human behaviour. The basic idea that comes from Fitts’ Law is the farther away a target is and the smaller its size then the more difficult it is for the user to correctly land on that target. In the formula, MT is the average time to complete the movement. The equation was originally developed based on participants … So this is both a basic equation, how to understand Fitts' Law, as a law that's still pretty darn useful. All right, lets unpack what all of this symbols mean. The above is the mathematical formula for Fitts’ Law. Fitt’s Law. To be honest, Fitts’ Law isn’t really a law at all. Fitts’s Law is an example of a principle in psychology which was developed from information theory (you can read more about this here [1]). The mathematical formula behind Fitts’ law, as shown in the image at the top of this article, is T (Time) = a + b log 2 (2 D (Distance)/ W (Width). For example, this law influenced the convention of making interactive buttons large (especially on finger-operated mobile devices)—smaller buttons are more difficult (and time-consuming) to click. For a given target acquisition task, e.g. It’s actually a descriptive model of human psychomotor behavior that’s written as an equation like this one. Fitts’ Law as it is normally expressed does not accurately predict performance when the width of the target varies from trial to trial. T as you might guess, that's the time to complete the appointed task, W, is the size of the target. Fitts’ law is widely applied in user experience (UX) and user interface (UI) design. Let’s take a closer look at that: Time is the amount of time that it will take the user to complete his or her movement. For example, can Fitts’ law describe user performance of pointing in Virtual Reality? Fitts’ Law itself and its application in Human Computer Interaction. Fitts's law (often cited as Fitts' law) is a predictive model of human movement primarily used in human–computer interaction and ergonomics.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. Fitts's law (often cited as Fitts' law) is a model of human movement in human-computer interaction and ergonomics which predicts that the time required to rapidly move to a target area is a function of the distance to and the size of the target. move the mouse to a certain point in the UI of an application and select it, Fitts's law desribes how the distance from start point to the target and the width of the target influence the index of difficulty (ID) of the task. Fitts’ Law can draw many conclusions, however, the summary is quite simple: “The time to acquire a target is a function of the distance to and size of the target.” Fitts's Law. We don’t need to understand it in detail. It describes the relationship between the difficulty of selecting a target and how big the target is and how far away it is. A&B are model parameters. The logarithmic relationship means that after some point Fitts’ Law will have diminishing returns. 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