When seventh-grader Ellie, who is having best-friend problems, and eighth-grader Jack, who is under tremendous pressure from his father, switch bodies and lives, they learn a great deal about themselves and the opposite sex.

Think of a secret that you're keeping from others. It shouldn't take long; behavioral scientist Michael Slepian finds that on average, we are keeping as many as thirteen secrets at any given time. His research involving more than 50,000 participants from around the globe shows that the most common secrets include: lies we've told, addiction or mental health challenges, a hidden relationship, financial struggles, and more. Our secrets can weigh heavily...