Dear Mr. Dad: My six-year-old son has suddenly begun cheating at games, at school, in sports—pretty much every chance he gets. This has come out of the blue. I can’t help feeling it’s a moral issue. How can I nip it in the bud?

A: If you hadn’t told me your son’s age, I’d have guessed it within a year or so. The good news is that he’s right on schedule for the little social experiment he’s conducting.

A very powerful thing happens in child development right around age six. Developmental psychologists call it Theory of Mind—the point when kids begin to truly grasp that other people experience the world from their own unique perspective, and that they don’t always know what’s going on in other people’s heads. Before that, kids have a kind of “universal mind” idea, believing that everyone sees and experiences things in the same way and shares the same knowledge.

Theory of Mind causes several things to happen. First, it’s the start of real empathy, understanding how others feel and why that might be different from what the child himself feels. It also opens opportunities for developing conflict resolution skills and valuing diversity.

Unfortunately, another common result of this leap in understanding is experimenting with lying and cheating. Once you realize that Mom and Dad don’t know everything—especially what you’re thinking—it’s time to try hiding candy behind your back, denying you have it, and feeling powerful in your ability to deceive.

Cheating is just a form of lying, so kids start doing it at the same age and for the same reasons. But cheating also has another incentive: competition. From the youngest age, kids get the message that losing is bad and that winning makes Mom and Dad proud.

As children move into later elementary and middle school years, peers begin policing each other, labeling and scolding cheaters. At that point, social self-preservation often kicks in and many kids stop cheating. But there are a few things you can do to encourage your child to start playing by the rules now.

If your child has a pattern of cheating, is there are reason? Is he under some kind of pressure to win? Also consider the difficulty of the activity he’s cheating at. Kids will often cheat when it’s too difficult for them to succeed within the rules. Could your family expectations be putting so much pressure on your child to perform that he is resorting to cheating to avoid disappointing you?

Nothing, however, speaks louder than the example you set. If your child catches you speeding or lying about his age so you can get a discount on something and you say, “Everyone does it,” you’ve just told him cheating is okay. Instead, “You’re right—I shouldn’t do that. Thanks for catching me,” can go a long way toward underlining the importance of reasonable rules.

If your child is caught cheating at school, take it seriously, but don’t act as if he’s on a slippery slope to a life of crime. Emphasize the positive (“I know you’re an honest person”) and encourage empathetic thinking (“What if everyone did that?”). At the same time, let him know that there are serious penalties for academic—and other kinds of —cheating. Harsh punishment, especially for first infractions, isn’t helpful in the long run.

At this point, try not think of your child’s cheating as some kind of moral cancer. It’s normal. But if the problem becomes chronic, talk to your child’s teacher or school counselor to see if a professional referral is called for.