I had recently read that too, but it was more specifically about the idea of willpower rather than decision-making fatigue per se. Here is the article where I had seen this, though going back to it, I don't see citations to the studies it's mentioning:

> If ego depletion does turn out to be wrong, it’s striking how seemingly well-established it became before more rigorous investigations dispelled the assumptions it rests on. The story of its rise and fall also shows how faulty assumptions about willpower are not just misleading, but can be harmful. Related studies have shown that beliefs about willpower strongly influence self-control: Research subjects who believe in ego depletion (that willpower is a limited resource) show diminishing self-control over the course of an experiment, while people who don’t believe in ego depletion are steady throughout. What’s more, when subjects are manipulated into believing in ego depletion through subtly biased questionnaires at the outset of a study, their performance suffers as well.

https://getpocket.com/explore/item/against-willpower

EDIT: It appears the studies are cited at the bottom of the article.

I certainly experience mental fatigue. I have a hard time believing that if I didn't know about it, I wouldn't experience it.