As marketers, we rely on data to guide our decisions. We run A/B tests. We use robust analytics tools. We find out where customers are converting, and where they're not. We know exactly what our customers are doing. But there's one major problem: we don't always understand why. If you're like most marketers, you've probably thought your job would be easier if only you understood what's actually going on inside your customers' heads. The only way to be sure what customers are thinking is to ask them. And the way to do that is by user testing.