In last week’s post, we discussed David Hogue’s third core principle of interaction design, learnability. Today I want to talk about a principle of interaction design that goes a long way in making users feel confident, comfortable and in control: predictability. Predictability, according to Hogue, means that all aspects of the interaction design should set accurate expectations about what will happen — before the user taps, swipes or clicks on something.

Principle 4: Good Interaction Design is Predictable.

“If you can accurately predict what’s going to happen in an interaction, it’s because the action you’re taking is understandable, clear, logical, and makes you feel confident.”
Robert Hoekman, Jr.

Predictability in interaction design can be measured pretty easily, and Steve Krug’s excellent book Don’t Make Me Think sums it up perfectly. Ask yourself if users will be able to answer these questions:

  1. Where am I?
  2. How did I get here?
  3. What can I do here?
  4. Where can I go from here?

Krug says that if you can drop a person into the depths of a site or application, ask these four questions, and get correct answers to all four, then you have:

  • provided a strong sense of place,
  • set the correct expectations, and
  • made it possible for people to accurately predict the outcomes of their interactions.

The sense of comfort that is created as a result is a critical factor in keeping people eon the site, fully engaged and moving forward. A sense of control — which is a hard-wired cognitive requirement in the brain — speeds task completion and makes people feel good about what they’re using, what they’re doing and what they’ll be able to accomplish.

Timeless UI Principles

The following infographic contains some interaction design principles to help you improve the predictability of your UI designs. Click or tap here for a larger, downloadable PDF version.

Infographic: Predictability in Interaction Design

The key takeaway here is that delivering a predictable, positive experience improves your chances of successfully matching the user’s expectations, along with the mental model they already have of how the experience should unfold. When what happens on the screen matches what they expect, they’re more confident, comfortable and happy. Which means they’ll keep visiting and using what you’ve designed.

Tune in next week for Principle #5! In the meantime, GIVE GOOD UX!

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