I ask this question because I KNOW they do. But I'm curious to see how many people believe this is true. Tesla quote - My brain is only a receiver, in the Universe there is a core from which we obtain knowledge, strength and inspiration. I have not penetrated into the secrets of this core, but I know that it exists. ~Nikola Tesla I personally know it's true after studying it for several years. Do you believe?
In their jumbled, fantastical way, dreams do give us an insight into what we ourselves are thinking about or (feeling our way along the contours of, in the dark).
Some psychologists hypothesize that dreams are simulations or rehearsals for situations we might encounter, and I understand that some research supports that idea. Sounds a bit improbable, given the far-fetched, nonlinear scenarios of most dreams. But if you spend a full day playing a video game, you might dream about it. And if you dream about it, then you might be better at playing it the next day. (That's my recollection of one such study.)
There are also anecdotes from mathematicians who reportedly dreamed solutions to conundrums that had baffled them by day.