What causes our brain to get “tired” and lose focus when thinking hard for extended periods of time like studying or thinking through a difficult concept?

Question

What causes our brain to get “tired” and lose focus when thinking hard for extended periods of time like studying or thinking through a difficult concept?

In: 120

Answer 1

[Veritasium on YouTube has a good video](https://youtu.be/UBVV8pch1dM) on this topic that explains the different types of thinking and the energy they take.