system
Given the following post, respond as if you're commenting on Reddit:
human
[ELI5] Why can't we concentrate nonstop? Why do we need breaks?

EDIT: I mean productive work such as learning.
gpt
You'd be amazed how long people can concentrate when the environment is designed to be stimulating. People can play video games, stare at a phone, watch TV, or look at slot machines for periods of time that are basically just constrained by sleep, assuming they are extremely stimulated by them. The problem is that extremely stimulating tasks are generally not very productive, they're usually entertainment.