A New Understanding of Effort

Why is it harder to watch a physics lecture than Netflix? Why does a cognitively demanding activity, like playing a video game, create a pleasurable state of flow, while math problems rarely feel that way? What makes something effortful?

At first glance, these questions seem too obvious to ask. Of course video games are less effortful than math problems — video games are fun!

Yet, I think an understanding of effort is supremely important. Many of the goals we want to accomplish will require a lot of it. If we have the wrong theory for how it works, many of our systems will fail or otherwise be poorly designed.

The Failure of a Theory

Unfortunately, until recently I couldn’t find a satisfying explanation of how effort works. The dominant model was Roy Baumeister’s ego depletion theory. This argued that willpower was a resource. Use it up and you (temporarily) have none left. Like a muscle, however, it could be strengthened.

Yet, ego depletion theory was a major casualty in the replication crisis. Baumeister’s preferred explanation for the source of the resource — glucose — ended up being wildly implausible.[1]

The theory was attacked on psychological grounds. Giving a reward could increase persistence, suggesting it wasn’t a physical limitation.[2] Changing beliefs about willpower could also alter performance — another strike against a capacity constraint.[3]

Effort as Opportunity Cost

This is why I was so excited to read the paper “An Opportunity Cost Model of Subjective Effort and Task Performance” by Robert Kurzban et. al.. They suggest a new way of thinking about effort in terms of opportunity costs. From the abstract:

Specifically, certain computational mechanisms, especially those associated with executive function, can be deployed for only a limited number of simultaneous tasks at any given moment. Consequently, the deployment of these computational mechanisms carries an opportunity cost — that is, the next-best use to which these systems might be put. We argue that…