But there are lies, and then there are lies. Hilfer assures me that Santa and the tooth fairy are not (necessarily) the stuff of future therapy sessions. Instead, they fuel kids’ imaginations and make holidays more magical. Children long to believe in these stories, and parents like me are only too happy to accommodate them. Coaxing children to lie in order to spare someone’s feelings—“tell Grandma you love the pair of socks she knitted for you even though they’re really scratchy”—is also perfectly acceptable, according to the pros. In fact, the ability to understand these kinds of “pro-social” lies is a positive developmental milestone for children, according to Victoria Talwar, an assistant professor at Montreal’s McGill University and an expert on children and lying. It shows they have developed empathy and have begun to understand that there is a world beyond them.

The experts were less reassuring, however, about what I have come to think of as lies of convenience. You know, telling your child you cannot afford to buy a $3 sack of polished stones at the science museum when the truth is that you just don’t want any more rocks at your house. Pretending to call Santa on your cell phone to alert him to bad behavior also apparently falls into the unacceptable category. Even though I think that what most parents lament about this particular white lie is that it can be employed effectively during only a few short months, it actually represents abdicating parental responsibility. “That’s asking Santa to do your job,” says Wendy Mogel, a child psychologist in Los Angeles. “That’s asking Santa to do your job. Santa’s job is to get down the chimney and eat the cookies. You have the courage to say ’no’ to your own child.” After absorbing that bombshell, I asked Mogel about the downside of false praise. She says that telling your child everything he or she does is great ultimately does them a disservice. We do this because we want our kids to be secure and to like us, she says, but plenty of research shows that external reward reduces intrinsic motivation. Better to ask them about their process—why they chose blue for their artwork or decided to make Mommy’s head square.

Like most parenting advice, the truth about lying is both slightly obvious and nearly impossible to follow. I’d like to think I’ve lied for the best of reasons—to make a holiday extra-special or because I really meant to leave work early and spend time with my child. But I’ve also lied because I was exhausted and wanted to avoid an argument. By 7 or 8, experts say, most kids understand the intentions behind a lie, which puts me right in the danger zone. So I’m going to try to stop lying to my daughter because I want her to trust me, and because I don’t want her to learn that lying is an effective strategy for dealing with the adult world. Even if that’s the sad truth.