(Mom.me) It’s every parent’s nightmare. You take your child to the park, look away for a few moments, and suddenly he’s gone.

What many parents take comfort in, however, is their trust that they’ve done a thorough job explaining “stranger danger” to their kids. An experiment conducted in August by Daybreak, a TV program in the United Kingdom, shows that parents need to think again.

In a controlled environment at a park in suburban London, the TV program enlisted a man—a vetted security guard with children of his own—to approach various kids, ranging in age from 5-11. He then told them that he had either lost his dog or his daughter. The kids were at the park with their moms, who were participating in the experiment and pretended to take calls on their cell phones.

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