Radio buttons, by their very nature, have only one option selected at a time. For the sake of consistency, it is important to have a default option when presenting the user with radio buttons. The current four candidates for U.S. president all have contribution pages on their websites that let users choose a contribution amount through radio buttons, but none of them have a default option for the contribution amount.

They not only misuse the radio button–they miss an opportunity to anchor users’ expectations for how much they ought to contribute to the campaign.

Take John McCain, for example. His form lets one choose $25, $50, $100, $500, $1000, $2300, $4600, or Other. A user coming to this page may have no idea what the average contribution amount is, nothing to base his decision off of. He may think that $100 is a generous contribution.

Imagine, instead, of the John McCain form filled in $100 as the default amount. At that point, the user may think “I really support John McCain–I’m going to give even more!”

This is not a matter of users making rational economic decisions. It is a matter of influencing the user. Humans are prone to judging situations in terms of what we’ve seen most recently and the candidates, by not setting users’ expectations, are missing out on a golden opportunity to raise funds.

Tags: Design, ui, Usability