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Predictability of a function

A little bit about usability: a good portion of designers do not understand the importance of predictability of a function. This short article is aiming to explain the underestimated role of making things as anticipated.

First, let's briefly define the term predictable. Dictionaries suggest synonyms like foreseeable, anticipated, expected, and more. Predictable means it is an entity's ability to be declared in advance and behaving the expected way. At the same time, it is related to standing in someone's expectations who interacts with an entity for the first time.

What is a function? In terms of user experience, we are referencing any singular process of some device or application. A function is a set of actions or short procedure processed by hardware or software. It is very close to a feature, yet it renders an uncomplicated outcome.

Predictability of a function in user experience is all about knowing in advance or feeling the upcoming event. Often, predictable means boring, but not when it comes to usability. People interact with products or services to achieve some goal. The designer's role is to allow the users to reach the goal smoothly. Meaning, the interface should be structured to get the desired result quickly and effortlessly. Unless, it is a product that is challenging those parameters, for example, a game.

Predictable is right and in place when the user works with a text editing tool or medical application. For example, the user clicks on a button, estimates, expects or knows what should happen next. Awkward, unpredictable behavior takes away the user from his goal. Interface elements, in the case of productivity-driven software, should clearly state the functionality behind them. The broken user experience rises from wrong product behavior if something random happens.

Planning the interface designer has to think about the positive and negative effects of the predictability. Using unexpected behavior designer has two simple outcomes: accurate and contradictory.

Accurate is when it is a planned surprise, but unforeseen. For the user's perception, something magical happens while the user achieves the desired result. So, in the end, it is perceived as positive.

But the opposite to that is contradictory, a destructive and sudden outcome. The outcome introduced a sudden unintended deviation from the user's flow. Such behavior is negatively perceived and leads to dissatisfaction. So, designing for unexpected behavior is a balance between right and contradictory. The unpredictable behavior has to be at a well-defined place to engage the user positively.

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