Learn about the interplay between user experience and product design.

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Previously, I wrote about the need for an information architecture (IA) framework for creating products. In this piece, I will decompose (simply and at a higher level) Fitts’s Law and its interplay with human-computer interaction.

Fitts’ Law is a model associated with the human movement which asserts that the time to acquire a target is a function of the distance to and size of the target — in other words, clicking on something far away or small takes longer than clicking on something close by or large. This concept has crucial implications for UX and product design. For example, it may help designers forecast how long it will take users to do specific tasks inside an interface and find opportunities to make user interactions more efficient.

Further, Fitts’s Law can be utilized to help optimize the positioning of UI components and content on a page or screen. As an illustration, if you want users to be able to click on a button swiftly, make sure that the button is large and close to the user’s current cursor position. On the other hand, if you don’t want users to accidentally click on something, such as an ad or a call-to-action that takes them away from the main activity they’re attempting to complete, make it small and/or far away from where their cursor is likely to be.

Fitts’s Law is fundamental to human-computer interaction, which is the study of how people use technological systems. For example, it claims that the speed at which a person can respond to an input device (such as a mouse) depends on at least the following factors: Nyquist rate and user interface layout.

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Background

Donald Hebb, a professor at McGill University at the time, made the empirical discovery that physical action can be deliberately controlled to achieve specified aims. It has been proposed, however, that human motor abilities evolved expressly for tool use and coordination, which would explain why these talents are so difficult to forget or fundamentally change.

Fitts’ Law is frequently used in the design of interactive systems. This is because physical input/output (I/O) tasks in these systems often require very small motions of the user’s hand or fingers; thus, designing them for speed and precision makes sense. However, some activities inside interactive systems, such as clicking an item in a list or selecting from a menu, involve considerable movements and may not precisely obey Fitts’ Law.

In this instance, designers should consider how users engage with their interfaces to deliver the best overall experience. Consider a web browser as an example of this interaction, which has a far more straightforward user interface than, say, an aviation cockpit monitor. This is because the mouse and keyboard may be more ideal for navigation than the various knobs and switches on the airplane’s instrument panel.

Consider what a variable may be in the context of Fitts’ Law (even more simplified in the context of this Law’s variables: the size of a movement that the user can achieve). This is, in essence, how speed and amplitude are related. Essentially, it states that if the variable (such as hand size) becomes smaller, more detailed movements with less effort are achievable. If the variable grows in size, fewer but wider strokes can be utilized for a given amount of force, perhaps resulting in increased speed and amplitude.

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How Fitts’ Law is employed in UX design

Typically, interface design begins with determining the purpose or task that users will be able to achieve. Fitts law is then applied to this goal to determine how efficiently users may move through the interface and achieve their goals. Finally, this data is used throughout the process, from mockups and wireframes to final product delivery, to produce an intuitive user experience suited to each activity.

For instance, one page can be devoted to listing various products on a website. When looking for a certain item, users will often begin by scrolling down the list until they discover what they are looking for. If, on the other hand, Fitts’ Law indicates that users are more likely to locate items on the left side of a screen where there is extra space available, then this information could be used in order to place all of the products in one column on the right-hand side, or even create smaller versions of each product listing for those who have limited viewing spaces.

In addition, when designing user interfaces, it is possible to consider additional elements such as cognitive loading, which refers to the amount of mental effort necessary to complete tasks, and heuristic processing (“rules” humans use while working). For instance, a large number of users who use computers may develop a habit of clicking on links first, sometimes even before reading the text that describes what those links lead to; this may be largely due to heuristic processing (which dictates that objects seen sooner are assumed to be important relative not just relevant).

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Parting Thoughts

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Anil Tilbe