design tip

Anticipate mistakes

To err is human; to forgive, divine. Alexander Pope, "An Essay on Criticism" People make mistakes, but they shouldn’t (always) have to suffer the consequences. There are two ways to help lessen the impact of human error:

  • Prevent mistakes before they happen
  • Provide ways to fix them after they happen You see a lot of mistake-prevention techniques in ecommerce and form design. Buttons remain inactive until you fill out all fields. Forms detect that an email address hasn’t been entered properly. Pop-ups ask you if you really want to abandon your shopping cart (yes, I do, Amazon—no matter how much it may scar the poor thing). Anticipating mistakes is often less frustrating than trying to fix them after the fact. That’s because they occurbefore the satisfying sense of completion that comes with clicking the “Next” or “Submit” button can set in. That said, sometimes you just have to let accidents happen. That’s when detailed error messages really come into their own. When you’re writing error messages, make sure they do two things:
  • Explain the problem. E.g., “You said you were born on Mars, which humans haven’t colonized. Yet.”
  • Explain how to fix it. E.g., “Please enter a birthplace here on Earth.” Note that you can take a page from that same book for non-error situations. For instance, if I delete something, but it’s possible to restore it, let me know that with a line of copy like “You can always restore deleted items by going to your Trash and clicking Restore.” The principle of anticipating user error is called the poka-yoke principle. Poka-yoke is a Japanese term that translates to “mistake-proofing.”