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Five ideas from HCI every product team can use

Five ideas from human-computer interaction research that still explain much of what goes wrong on a screen, each with its original source and how to use it.

Research

1. The two gulfs: doing, and knowing it worked

Hutchins, Hollan and Norman described two distances between a person and a system. The gulf of execution is the distance between what the person wants and the actions the interface offers. The gulf of evaluation is the distance between what the system did and what the person can perceive and understand of it.

In practice: when someone gets stuck, ask which gulf they’re in. A control nobody finds is a gulf of execution; fix its label, its placement or what it looks like it does. A confirmation that vanishes, or that a screen reader never announces, is a gulf of evaluation. The task worked, and the person can’t tell. Fix it with feedback that stays, and that everyone can perceive.

Hutchins, E. L., Hollan, J. D. and Norman, D. A. (1985). Direct manipulation interfaces. Human–Computer Interaction, 1(4). Norman, D. A. (1988). The Psychology of Everyday Things, later The Design of Everyday Things.

2. The cognitive walkthrough

A walkthrough steps through a task from the user’s point of view and asks four questions at every step. Will they try to achieve the right effect? Will they notice the right action is available? Will they connect that action with the effect they want? After the action, will they see that they’re making progress?

In practice: pick one task, open the product where a new user would start, and ask the four questions at each screen before you click. Write down the step and the question that got a “no”. A walkthrough needs no participants, so a designer or engineer can run one on a pull request before it ships.

Wharton, C., Rieman, J., Lewis, C. and Polson, P. (1994). The cognitive walkthrough method: a practitioner’s guide. In Nielsen, J. and Mack, R. L. (eds), Usability Inspection Methods. Wiley.

3. Heuristics, and more than one reviewer

Nielsen and Molich had people judge interfaces against a short list of principles, such as keeping people informed about what’s happening and helping them recognize and recover from errors. Single reviewers missed many of the problems that a few reviewers found together.

In practice: have three to five people review the same screens on their own, then merge their notes. Each one finds problems the others miss, and the problems several of them found are the ones to fix first.

Nielsen, J. and Molich, R. (1990). Heuristic evaluation of user interfaces. Proceedings of CHI ’90. ACM.

4. Fitts’s law: small, distant targets cost more

Fitts showed that the time to reach a target grows with its distance and shrinks with its size. A small button far from where the pointer is takes longer to hit.

In practice: put the controls people use most where the pointer or thumb already is, and make them large. WCAG 2.2’s minimum target size applies the same idea: 24 by 24 CSS pixels or enough space around the target, for people with tremors or limited dexterity. 2.5.8 Target Size (Minimum)

Fitts, P. M. (1954). The information capacity of the human motor system in controlling the amplitude of movement. Journal of Experimental Psychology, 47(6).

5. Recognition over recall

Recognizing something you’re shown is easier than recalling it from memory. Interfaces that show the options, keep earlier answers and let people copy instead of remembering ask less of everyone, and help people with memory or attention disabilities most.

In practice: show options instead of asking people to type them, keep what they entered when they go back, and let password managers fill in fields. The same idea is behind two WCAG 2.2 criteria: a process shouldn’t ask for what someone already entered, and signing in shouldn’t depend on remembering or transcribing. 3.3.7 Redundant Entry, 3.3.8 Accessible Authentication (Minimum)

Nielsen, J. (1994). Enhancing the explanatory power of usability heuristics. Proceedings of CHI ’94. ACM.

What these methods can’t tell you

Each of these predicts where people may struggle. None of them measures how people feel, or how often a problem happens in real use. They’re inspection methods. They show you where to look; research with the people who use your product tells you what each problem costs them.

See it on a product