User experience laws

There exists a set of principles governed by human psychology that influence how we perceive and use systems. A body of these principles have been summarized in Laws of UX, which outlines a collection of best practices for building user interfaces. Here, we outline a few of them.

• Jakob's Law states that "users spend most of their time on other sites". In effect, through the use of other sites, users learn to expect how a site (or an application) works, and tend to expect such behavior also from new applications.

The practical application of Jakob's law would be to draw inspiration and learn from others when designing applications. In practice, one can draw inspiration from -- and use -- common design systems, which leads to a situation where applications share design practices and application usability in general improves as users' prior expectations are met.

• Law of Common Region, Law of Proximity, Law of Similarity, and Law of Uniform Connectedness are all related to whether and how users perceive that shown objects are grouped. First, when components are located within the same closed region, they are seen as a group. Second, when components are close to each other, they are seen as a group. Third, when components look the same, they are considered to be a group. Fourth, components that are visually linked are more likely to be seen as related to each other.

The practical application of these four laws from the design point of view is to consider what information is linked and to design applications so that the design provides cues of related information. As an example, in an application used to list contact details, individual contact details could be shown within a Card widget with a specific style that all contact details would share, and the contacts could be placed within a region with clear boundaries. Moreover, the contact information of different individuals could be close to each other in the application.

• Fitts's Law states that the time to move to a target is a function of the distance and size of the target. Fast movement to small targets lead to higher probability of errors (e.g. misclicks), while slow movement to large targets lead to smaller probability of errors.

The practical application of Fitts's Law from the design point of view is to design the applications so that interactive elements have sufficient space around them and that the interactive elements are sufficiently large. With sufficient space in terms of a margin, even in the case of a misclick, the user would not be directed to an incorrect location. Similarly, with sufficient size of an interactive element (padding, font size, etc), the likelihood of misclicks reduces.

• Doherty Threshold states that productivity increases when the user does not have to wait for the computer and the computer does not have to wait for the user.

The practical application of Doherty Threshold is to design the application so that the user does not have to wait for actions to be completed. In the case of heavy or long-lasting operations, the application can still react to users' actions by e.g. showing a progress bar or a loading animation.