Interesting; another thing I've heard of is called "sleep paralysis".

A person finds they can't move; like they are disengaged from operating their body I've heard.

Also you get situations where someone wants to shout out but they seem voice-paralysed; I've heard.

But sometimes a situation occurs where (I've done this) one calls out in one's dream and wakes up as one really calls out.

Another strange thing: one's brain might create illusions: I thought a pilot light was still on on a dish-washer machine at night; but it wasn't; it was on a heater nearby. But how come my brain put the on-light on the wrong object? And how come I was sure two people were moving near a distant rock; when it was just two signposts?

In both cases my own expectation of what I expected to see may have coloured what I "saw".

I've heard that the eye only vaguely defines things but a small region exactly defines things; perhaps one's brain fills in the missing detail sometimes according to expectation rather than actual sighting where detail has been scanned with a margin for error?

-Alan