Fitts's Law. First of all it is not Fitts Law. The name of the famous researcher is Paul Fitts, so one should be careful on spelling. Fitts's Law is basically an empirical model explaining speed-accuracy tradeoff characteristics of human muscle movement with some analogy to Shannons channel capacity theorem. Today, with the advent of graphical user interfaces and different styles of interaction, Fitts Law seems to have more importance than ever before. The early experiments on pointing movements targeted the tasks that might be related to the worker efficiency problem, such as production line and assembly tasks. They were not targeted to HCI field because there was no GUI.
A. Fitts started his work making an analogy of the human motor system to the well-known Shannon's channel capacity theorem. Here, MT represents the movement time to hit the target, a and b are empirically determined constants. Figure 2. Figure 3. . (2a) Welford, suggested a better model by separating A and W into two terms. Fitts's. Giving You Fitts - Jensen Harris: An Office User Interface Blog. One of the most well-understood and salient principles underlying the ergonomics of graphical user interface design is Fitts' Law. Named for Paul Fitts, a psychologist at Ohio State University, Fitts' Law is a mathematical model of fine motor control which predicts how long it takes to move from one position to another as a function of the distance to and size of the target area.
Papers outlining what became known as Fitts' Law were published in 1954 and 1964. Fitts himself was an expert in aviation psychology, and he developed his research around more ergonomic layouts for cockpit instrumentation as a way of increasing aviation safety. You can read more about the early history and mathematics behind Fitts' Law on Wikipedia. Fitts' model proved especially relevant to the early research on computer input devices performed in the late 1970s. Although there's a great deal of subtlety to Fitts' research, what became known as Fitts' law is a fairly simple intuitive concept. Summary. Fitts' Law and Infinite Width. Fitts' Law is arguably the most important formula in the field of human-computer interaction.
It's.. Time = a + b log2 ( D / S + 1 ) .. where D is the distance from the starting point of the cursor, and S is the width of the target. This is all considered on a 2D plane relative to the axis of movement. Years of experimental results have proven Fitts' law time and time again: Fitts' law has been shown to apply under a variety of conditions, with many different limbs (hands, feet, head-mounted sights, eye gaze), manipulanda (input devices), physical environments (including underwater!) It's not exactly rocket science, as Bruce Tognazzini points out: The time to acquire a target is a function of the distance to and size of the target.
So, to make navigation easier, you either put clickable items closer together, or you make the clickable area bigger. Here's one thing that puzzled me. They aren't significantly larger. Where does the menu go in a multiple monitor scenario? A Quiz Designed to Give You Fitts. NN/g Home AskTog Columns A Quiz Designed to Give You Fitts Ask Tog, February, 1999 (Turkish translation available at So you think you are an interaction designer?
If you're not an interaction designer, but you know one—or you are thinking of hiring one—slip them just the questions, and see how well they do. These questions and answers assume that you have total control over all screen real estate, the OS, etc. If you are new to matters Fitts, take the quiz before looking at the text the follows anyway. The Quiz You may want to read through all the questions (but not the answers!) No tricks are hiding within. Microsoft Toolbars offer the user the option of displaying a label below each tool. If you can’t answer the last question, you are going to have all kinds of trouble with the rest. Microsoft sort of has an excuse. What has happened at Apple is a little more mysterious. The Answers Question 1 Here are two answers. Question 2 Question 3. Improving Usability with Fitts’ Law.
Back in 1954, psychologist Paul Fitts published an article the detailed his theory on human mechanics as it pertained to aimed movement. It was Fitts’ observation that the action of pointing to or tapping an target object could be measured and predicted mathematically. Fitts stated that the size of the target object along with its distance from the starting location could be directly measured, allowing him to model the ease at which a person could perform the same action with a different target object.
In 1954, this theory had no application for computers yet; however, it shouldn’t take a modern designer long to discover the powerful meaning this formula has in the context of user interfaces. Because of this, Fitts’ law has become a staple in the field of human-computer interaction (HCI), and has become one of the most accepted guidelines in the industry. Fitts’ law, at its simplest form, is common sense. The bigger an object and the closer it is to us, the easier it is to move to.