In our research, we asked a group of undergraduates to work on word puzzles. Before they began, we had them tell us how exciting and enjoyable they thought the task would be. Then they read a statement that framed the task as either personally valuable or of neutral value.

Those who read the first statement, and who also thought the task would be enjoyable, solved the most problems. Moreover, their work didn’t flag, meaning they did not perform best simply because their interest made them want to work on it longer, thereby causing them to solve more problems. Instead, their engagement was more efficient. In other words, they were “in the zone.”

We then wanted to see if this increased performance would make people feel fatigued, or if their high interest in the task would maintain their mental resources. In a follow-up study, we assessed undergraduates’ anticipated enjoyment of the task as well as its personal value. After working on a set of word puzzles, they squeezed a spring-loaded exercise grip for as long as they could, a task commonly used in psychology experiments to assess mental exhaustion. Much like the self-control needed to stay on task when we would rather do something more fun, resisting the urge to let go of your grip when it becomes uncomfortable also requires self-control. And that exertion of self-control is mentally fatiguing.

We found that people who thought the puzzle was highly enjoyable and highly important not only performed among the best, again, but they also squeezed the hand grip the longest. In other words, they solved the most problems, and it was not mentally exhausting for them. In contrast, those who were uninterested in the task generally performed worse, and were mentally fatigued by the effort.

Some of us are lucky enough to find our goals interesting — but that won’t always be the case. If interest is critical, how can we take a boring activity and make it interesting?