system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What exactly happens when we "zone out?"
gpt
There are quite a few factors to the whole zoning out thing. Boredom, stress, intense focus, or just thinking in your own head.
Also that there are 2 types of zoning out: being aware that you're zoning out and being unaware of it.
But the gist of it is, (paying no matter to what triggered the zone out, as it could be any number of things, and is irrelevant.) 
SO, the beginning of a self aware zone out: Your mind snags a piece of information, that stood out to you, or you experience a minor revelation off that that one piece of information.
Then, a number of connections piggy backing the original are now being made. Fairly rapidly too. This is now taking up most, if not all, of your attention, and since you're awake and concentrating on something in your head, not looking at anything, it causes that weird out of focus vision.