Given this tendency, it makes sense that we often rely intuitively on external rules to help ourselves out. A few years ago, Dan Ariely, a psychologist at M.I.T., did a fascinating experiment examining one of the most basic external tools for dealing with procrastination: deadlines. Students in a class were assigned three papers for the semester, and they were given a choice: they could set separate deadlines for when they had to hand in each of the papers or they could hand them all in together at the end of the semester. There was no benefit to handing the papers in early, since they were all going to be graded at semester’s end, and there was a potential cost to setting the deadlines, since if you missed a deadline your grade would be docked. So the rational thing to do was to hand in all the papers at the end of the semester; that way you’d be free to write the papers sooner but not at risk of a penalty if you didn’t get around to it. Yet most of the students chose to set separate deadlines for each paper, precisely because they knew that they were otherwise unlikely to get around to working on the papers early, which meant they ran the risk of not finishing all three by the end of the semester. This is the essence of the extended will: instead of trusting themselves, the students relied on an outside tool to make themselves do what they actually wanted to do.