We all think we know our kids—their moods, their feelings, maybe even a little of their inner life. But do we? Researchers at UC Davis aren’t so sure. Kristin Lagattuta and her colleagues at Davis’ Center for Mind and Brain found that when it comes to kids under 7, dads and moms generally believe that their children are happier and less worried that they actually are.

This is pretty consistent with other studies that have found that parents’ assessments of our children are a little out of whack with reality. For example, our children are rarely as smart as we think they are, and they don’t do as well on math, language, and IQ tests as we think they do. This is what Lagattuta calls a “positivity bias.”

What’s the big deal? Well, because researchers have assumed that children under 7 can’t accurately describe their emotions, they’ve had to rely on parents to do the describing. But the wisdom of that approach is being questioned.

Of course, there’s nothing malicious about this—in fact it’s quite the opposite. We’re describing our children the way we want them to be, not the way they actually are. That’s fine in some circumstances, but if a child needs help, healthcare and mental health professionals need accurate information, not wishful thinking.

The study was published in the Journal of Experimental Child Psychology and was conducted by Lagattuta, post doctoral researcher Liat Sayfan, and  a former Davis grad student, Christi Bamford. They asked children 4-11 and their parents about a number of issues that frequently make kids anxious, such as being scared of the dark and worries about something bad happening to a family member.