Steven Spielberg is just a big kid. His films celebrate the childlike innocence that lets people experience amazing things. Think E.T. and Jurassic Park, even Poltergeist and Hook. He's done his share of darker, serious films for sure, but he revels in the joy of discovery and is masterful at depicting that on the big screen.
Close Encounters is no exception. Barry sees the aliens as friendly visitors well before the finale reveals their search for companionship. Roy's a childlike, Pinocchio-loving guy. He loves his train sets and plays with his mashed potatoes. That playful innocence allows him to see the UFOs with a sense of awe that other adults, like Ronnie, can't. He's ultimately rewarded with a new understanding of the universe and his place in it.
Even the aliens have wide-eyed, searching expressions, and many of them look like small children. It's no accident that the two people we see visited by the extraterrestrials are Roy and a three-year-old. Roy's not stuck in old ways of looking at things, which the film suggests is a recipe for never being able to learn something new.
Questions About Innocence
What does the film suggest about the dangers of being grown-up?
What innocent assumptions does Barry make about the UFOs?
How do the alien characters radiate innocence, and why is this important for the film thematically?
Chew on This
Lacombe's character combines innocence with scientific inquiry, suggesting that scientific pursuits are an extension of our natural, childlike curiosity. If he'd been corrupted by skepticism, the encounter wouldn't have happened.
Innocent wonder is all well and good, but in the end it was hard science that enabled the close encounter to be successful.