In an interview with Harvard Business Review, psychologist, researcher, and author Daniel Gilbert discussed how managers can motivate their employees. Although he was speaking to a business audience, his answer applies to many different relationships—parents and children, leaders and followers, mentors and protégés, husbands and wives.

We know that people are happiest when they're appropriately challenged—when they're trying to achieve goals that are difficult but not out of reach. Challenge and threat are not the same thing. People blossom when challenged and wither when threatened. Sure, you can get results from threats: Tell someone, "If you don't get this to me by Friday, you're fired," and you'll probably have it by Friday. But you'll also have an employee who will thereafter do his best to undermine you, who will feel no loyalty to the organization, and who will never do more than he must.

It would be much more effective to tell your employee, "I don't think most people could get this done by Friday. But I have full faith and confidence that you can. And it's hugely important to the entire team." Psychologists have studied reward and punishment for a century, and the bottom line is perfectly clear: Reward works better.