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

Thinking hard takes resources – time, energy, attention. Our brain evolved in an environment where the most productive activities involved physical or social effort, and so our emotions and urges are made to encourage those activities.

Working quietly on abstract tasks in a climate-controlled room is not a situation our brain evolved for. Our brain wants us to instead do things that make it feel productive, like eating, exercising, or socializing. These all would be the most important things for our pre-civilization ancestors to do, but many modern tasks do not require that sort of activity.