In this section, we’re going to talk about how the design of something makes it easier or harder to click on. I am going to start by giving you an example from web-based email clients. What’s the big difference between how these two e-mail clients implement the button for writing a new email.

Which system makes it easier for users to write a new message? Based on just the button size alone, we can probably say it’s the one on the left. How can we be so sure?

Well, it’s all about Fitt’s Law. Fitt’s Law states that it’s faster to hit larger targets closer to you than smaller targets further from you. Now you’re thinking that it should be easy enough to go off another equally apparent statement, make a law about it that you can attach your name to. The thing is, Mr. Fitt’s didn’t just make the law. He backed it up with science. Making an equation that explained how much easier it would be depending on all the variables.

We don’t care so much about the equation, we do care about the implications of the law.

The brake pedal in cars is bigger than the accelerator pedal. It’s also closer to you and that makes it faster and easier to hit in an emergency.

The button for switching on heavy machinery is small and recessed. The button for stopping it is large and prominent. You don’t want people starting machines by accident. You do want them to be very easy to stop if there’s a problem.