Assuming the intelligence of the reader is like telling a joke into a void. It's very tempting to yell "did you get it?" minutes later, because we don't get any response back. At least, not until we get reviews.
I came across this, and found it helpful.
How do we know we can trust our readers? Well, remember that these people are readers. Sometimes, when I'm out in the world, I don't exactly have a whole lot of faith in people's intelligence (I work retail). But people who read books for fun tend to be on a higher level than those who don't. They will get it.
When in doubt (and especially when you're 100% confident), always find someone willing to read your work, and get their opinion.