A system is useless if it can’t motivate people to use it. Your interfaces must be clear and appealing, your tasks must be satisfying and rewarding, and your games must be fun.
Here is a way to evaluate a system’s ability to recruit use, or human attention. Let’s take any web interface and task. Now let’s post it as a job on Mechanical Turk and see how much we need to pay people to use the interface to complete the task. The less we have to pay workers, the better the interface and task.
For instance, in this figure we gave users a button-clicking task (in the Fitts’ law style). We tried three button sizes, small, medium and large. On the X axis is how much we paid users. On the Y axis is how much use the interface received. You can see that users indeed prefer clicking on large buttons to small buttons, and by how much. But the exciting part is that if you measure the horizontal distance between the curves, you can see how much money the interface variation is worth to users!