Radio buttons, checkboxes, affirmative choices, and consents

Here are some notes about radio button and checkbox defaults for times when you need an affirmative answer.

Affirmative choices

The Nielsen/Norman Group (no relation) has an interesting article on radio buttons by Kara Pernice. Its advice is sound, but I want to note a case where there could perhaps be even more obviousness.

The next time you design a radio button interface, I'd like to advise you to think about an additional choice, which is essentially a default choice representing that a choice is not made.

Radio buttons provide for a mutually-exclusive choice. For instance, an airline serves two meals to first-class customers, one with pasta, one with rice. You can only pick one.

But this hides the implied third choice, which is not to have any meal. Better:

This may become important for legal requests for a formal, affirmative choice. For example, a health survey might ask:

But this doesn't allow the choice to say neither No nor Yes. Also, suppose you are a healthcare company that asks this question, and you don't want to be blamed if the user gets the wrong treatment according to this answer. The user might say: I was in a rush and took all of the default answers; the form reported this answer as "No," but it was actually "Yes."

Some people try to solve this with a form where neither choice is indicated by default, and the user is forced to choose one or the other:

I don...