Good luck proving that conscious will has any effect on the world whether waking or sleeping. People report that it does, and that's all we are sure about.
I wasn't really talking about "free will" or anything so airy; more about 1. your predictive model of your own behavior lining up with your actual behaviour; and 2. your predictive model of the causal effects of your behavior lining up with the actual observed world.
In dreams, neither of these are true: "you" don't behave the way you'd expect of your waking self, and the things "you" do don't result in what you'd expect out of the real world.
Re the last sentence. I have in fact deliberately behaved in ways I never would in life, in a lucid dream; and flown around which doesn't work in real life. Did you swap negative for positive.
That's not ego-dystonic decision-making; that's just different things being possible in the embodied environment and you being aware of that.
That is: you can fly in a dream; you can't fly in real life. But if you could fly in real life, you probably would. Therefore, it isn't shocking to "watch yourself" decide to fly, if flying is obviously an option.
Consider, by contrast, ripping your own limbs off. Perfectly possible in reality, but nobody does it. If you did it in a dream, you'd wonder why "you" wanted to do that. It wouldn't make sense for you to make that decision, so probably "you" aren't you at the moment.
You might try some stuff, e.g. stepping off a cliff in order to fly, only if you're really quite sure you're in a dream. But "being sure you're in a dream" means "being sure your actions have no long-term consequences in reality", which allows many more things to be ego-syntonic.
Actually, every decision you make while asleep is different from the one you'd make while awake. The mind is less organized; different parts of the brain are active. See the studies re EMG suppression of various parts of the brain, and the effect of that on artistic ability for a close parallel.
Rarely - you can recapture that very different way of being while awake and have skills you never had before.
There are ways to communicate from the REM state back to the real world used in research on lucid dreams:
> Previously to sleeping, volunteers like Worsley agreed on preset eye movements they would perform once they achieved lucidity in their dreams, which La Berge could record in the lab.
In dreams, neither of these are true: "you" don't behave the way you'd expect of your waking self, and the things "you" do don't result in what you'd expect out of the real world.