Why do humans procrastinate? A neuroscientist explains.

Tax Day just came and went. It is the same day every year (give or take), and people have the information they need to complete their tax returns months before this deadline. And yet, in spite of this, past trends suggest that nearly a third of tax returns were filed in the month prior to this recent deadline, over a third of those in the final week.

Taxes are an annual event, and may be uniquely aversive in any number of ways, but this example offers a window into a broader tendency we all share to different degrees. When we have a task to complete – particularly one that isn’t due in the immediate future – we tend to wait until close to the deadline to work on it, occasionally scrambling to complete it in time. Why do we do this? Why do we procrastinate?

I’m going to put off answering this question for a moment and instead start with a more fundamental one: Why do we do anything? Or, more specifically, why do we do anything that is demanding? All things being equal, we generally don’t like exerting mental or physical effort, so why not just avoid these entirely? The reason is obvious: getting the things we want, and avoiding the things we don’t want, requires effort. As Teddy Roosevelt said, “It is only through labor and painful effort […] that we move on to better things.” For us, those better things can happen soon after we complete a task (e.g., getting paid, impressing our peers) or can accrue over the longer term (e.g., career success, positive reputation).

But it’s not enough for these incentives to simply exist for them to affect our behavior. No, we have to be mindful of and care about those incentives for them to change how much effort we decide to invest. After all, we wouldn’t go out of our way to complete a task if we felt like the reward was inconsequential, or if we didn’t know that it would be rewarded. This may seem obvious, but it is likely to be critical for understanding procrastination.

Choosing to overcome a barrier comes naturally to us when we are escaping an imminent threat or chasing a nearby ice cream truck. When the potential rewards and the potential threats are tied to a deadline further into the future, they have less of a pull on us. We simply care less about carrots and sticks the more distant they feel, and that makes it harder for us to muster the necessary effort, especially when we are often surrounded by less distant-seeming carrots (from tasks that offer more immediate rewards to distractions like Twitter and Instagram).

The fact that more immediate incentives feel more salient to us is one part of why we put off performing tasks, but another part has to do with the kinds of effort that these tasks require. In general, completing an assignment for class or a project for work is not as straightforward as lifting a weight. These tasks require planning, which means thinking through all of the possible approaches to completing the task and choosing between them, something we generally don’t enjoy doing. These upfront planning costs may make starting a task particularly aversive, and contribute to other negative feelings we have about embarking on that task (like self-doubt).

Once we settle on a plan, we still have to complete all of the steps we planned before we reach our ultimate goal. Each of these subtasks requires us to exert some effort, but the reward for that effort only comes once the entire task is complete. It is not clear how procrastination is influenced by the subtasks required, but their presence can contribute to our desire to procrastinate in at least two ways. First, we may be demotivated each time we perform a subtask without being rewarded. Second, the breaks between subtasks create opportunities for us to succumb to temptation by nearby carrots (e.g., check social media), which then requires us to exert additional effort to refocus our attention on the next subtask.

When you put all of these factors together, it starts to make sense that we are more likely to work on a task when we are closest to a deadline (when the carrots and sticks are most salient), and that we tend to put off the task as a whole rather than spread that task out into more manageable pieces over time.

Understanding these mechanisms can also help us understand ways of avoiding procrastination. For instance, if we reward ourselves for completing subtasks, then we can make the eventual reward seem less distant while also increasing our motivation to continue with the next subtask. Recent work shows that this exact approach – which combines an old idea from psychology called shaping with newer ideas of how to keep people engaged with a video game – is effective at getting people to procrastinate less. While this method has yet to be applied to our everyday tasks, it is reasonable to assume that researchers will get around to doing so. Eventually.

Amitai Shenhav is assistant professor of cognitive, linguistic and psychological sciences at Brown University. His research is focused on examining the computational and neural mechanisms at the intersection between decision-making and cognitive control, with a particular focus on how people weigh the costs and benefits of engaging in cognitively demanding tasks.