When I was in fifth grade, I had a teacher who gave a daily homework assignment where we were supposed to bring a progress report home for our parents to sign, indicating that they'd seen it, and bring it to class the next day.
Being the scatterbrained 10-year-old I was, I almost always forgot to bring this progress report home to my parents. The following morning, my teacher would chastise me, in front of the whole class, for not listening to her simple instructions. Instead of being motivated by this to do better, I decided to avoid the problem entirely, by faking sick—exaggerated coughing, eating hot peppers to raise my body temperature, the whole nine yards—on the days I forgot to bring the progress report home.
Looking back on this time in my childhood—and on the many others when I lied to my parents for, ahem, less innocent reasons—I've assumed my parents just had to know I was lying and were just placating me to make me happy, or to avoid prying into things I wanted to hide from them. Really, I was, and still am, a terrible actor with an even worse poker face. There's just no way I was as convincing as my success rate would suggest.
But, it turns out there may have been stronger forces at play. The truth is, according to researchers at Brock University in Canada, parents are just really bad at spotting when their kids are lying. Their study found that, when it comes to their own children, parents could only detect a lie 8 percent of the time, thanks to an inherent "truth bias" parents have towards their kids. Other parents and childless adults who were unrelated to a given child, however, were four times better at detecting a lie. This truth bias, researchers have speculated, may come from the desire to maintain the delicate homeostasis that makes parent-child relationships successful.
"Parents may be less vigilant in detecting their children's lies for fear of disrupting a trusting relationship," writes the study's lead author, Angela Evans.
So parents, make sure to self-correct for this truth bias the next time your youngster insists he has the stomach flu for the third week in a row, or your teen tells you his friend's house party will totally have parental supervision. And kids, if you're reading, sorry for snitching.
Zach Verbit is an Editorial Intern at Parents Magazine who thinks that Liar Liar is Jim Carey's best movie.