Explorable Interfaces

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Principle: Give users well-marked roads and landmarks, then let them shift into four-wheel drive

Mimic the safety, consistency, visibility, and predictability of the natural landscape we’ve evolved to navigate successfully. Don’t trap users into a single path through a service, but do offer them a line of least resistance. This lets the new user and the user who just wants to get the job done in the quickest way possible a “no-brainer” way through, while still enabling those who want to explore and play what-if a means to wander farther afield.

Principle: Sometimes you do have to provide deep ruts

The earlier your users are on the experience curve, the more you need to guide them. A single-use application for accomplishing an unknown task requires a far more directive interface than a habitual-use interface for experts. The deepest ruts are wizards.

Principle: Offer users stable perceptual cues for a sense of “home”

Stable visual elements not only enable people to navigate fast, they act as dependable landmarks, giving people a sense of “home.” A company logo on every page of a website, including every page of checkout, all enabling the user to escape back to the home page, makes users feel safe and secure. Paradoxically, such cues make it more likely that people will not escape back to the home page, secure in the knowledge that they easily can.

Principle: Make Actions reversible

People explore in ways beyond navigation. Sometimes they want to find out what would happen if they carried out some potentially dangerous action. Sometimes they don’t intend to find out, but they do anyway by accident. By making actions reversible, users can both explore and can “get sloppy” with their work. A perfect user is a slow user.

Principle: Always allow “Undo”

The unavoidable result of not supporting undo is that you must then support a bunch of confirmation dialogs that say the equivalent of, “Are you really, really sure?” Needless to say, this slows people down.

If you fail to provide such dialogs, in the absence of undo, people slow down even further. A study a few years back showed that people in a hazardous environment make no more mistakes than people in a supportive and more visually obvious environment, but they work a lot slower, taking great care to avoid making errors. The result was a huge hit in productivity.

We usually think of the absence of Undo as being the sign of lazy programming, but sometimes people do it on purpose. For example, some ecommerce sites want to make it hard for you to take things back out of your shopping cart once you’ve put them in there. This turns out to be a backwards strategy: An ecommerce study we did at the Nielsen Norman Group looked at what happens when merchants make it really easy to take things out of shopping carts. As might be expected, people visiting these merchants were much more willing to throw things in, figuring, “oh, well, I can always take it back out later.” Except they didn’t take them back out, because the deletion rate was no different. These user just bought more stuff.

Principle: Always allow a way out

Users should never feel trapped inside a maze. They should have a clear path out.

Cancel & Wizards

Cancel is particularly import in Wizards. Let people leave at any time, but make sure to tell them where they can finish the task later on. When you user-test, bring back two weeks later the same people whom you had cancel in the middle of a task and ask them to continue. Watch where they browse. If they browse to two different places in your menus, consider putting the function both places.

Principle: Make it easy and attractive to stay in

A clear, visible workflow that enables people to understand where they are and move either backward or forward in a process will encourage people to stick with a task. Consider, as an example, a multi-step checkout procedure. Making the navigation visible by putting each step on a clearly-labelled tab will let people know where they are in the process. Clicking an earlier tab should allow people to jump back to correct an error or just change their mind by, for example, selecting a different delivery address. They should then be able to click on the tab they were originally on and resume their forward movement. When you either forbid people to move back or destroy all subsequent data if they do, they will not be happy with you. Even if they decide to grit their teeth and continue with the current sale, they are unlikely to ever return.