Coffee machine apparently unsure user really wants coffee

Here’s a funny post from F My Life:

Today, at the bank, I went to get some coffee from their machine. I gave it my money and pressed the buttons but nothing was happening. After banging on the machine for ten minutes and calling a teller over, a little boy reached up on his tippy toes to press the giant green START button for me. FML

It’s easy to laugh at the author if you don’t look too closely, but there are a few usability lesson in this story:

First, the user already signaled the machine that they wanted to start by putting their money in. Under what circumstances is a customer going to put money into a vending machine when they don’t want to buy something?

Second, once a user takes an action they think will produce a result, they’ll tend to disengage and wait for it. It generally doesn’t matter how big your button is or what text you display—the user won’t see it.

Third, if the expected result doesn’t happen, they’ll probably do what this person did and assume whatever they’re using is broken instead of looking for clues to what they might have done wrong.

It seems like they had perfectly reasonable expectations: put money into a vending machine, select what they want, and get it. Having a start button, no matter how big it is, is inconsistent with our mental model of a vending machine. Even giving the designers every possible benefit of the doubt—that their target user somehow has no mental model of vending at all—it’s still an unnecessary step that should have been left out.

Proposed solution: figure out what the user’s expected result is for each action is and give it to them. Don’t get clever, and don’t expect them to read anything, especially when you break a very common mental model. Don’t break them unless you have a really, really good reason.