This is the second Tip of the Week contributed by Ayelet Fishbach, whose book Get It Done: Surprising Lessons From the Science of Motivation was just published. 

“What beautiful music!” I exclaim as my 9-year-old son practices violin. He’s used to this praise; I give compliments like that most days. But every once in a while I skip it, and when I do, I can see the disappointment on his face when he’s finished. 

Am I a bad mom? Conventional wisdom says that consistency is key to parenting, since it enables your child to predict how you’ll react, leading to good behavior. And it’s true that children need some level of predictability in their lives, particularly when it comes to discipline. 

But research suggests that inconsistent gifts and praise can have a greater effect on motivation. While we all like to live in a predictable world, we often respond more strongly to unpredictable rewards.

In one experiment, my colleagues and I told participants they’d be paid if they could drink about one-and-a-half quarts of water in 2 minutes or less. In one condition, we offered people a $2 fixed reward. In another, there was an uncertain reward of either $2 or $1. The certain reward was a better deal, yet many more people successfully met the challenge when assigned an uncertain reward. Resolving the uncertainty—whether they would win $1 or $2—was significantly more motivating than winning $2 for sure.

There are several reasons why uncertainty is motivating. First, what scientists call “intermittent reinforcement”—rewarding behavior on some but not all occasions—makes it harder to know when rewards will show up. If you very often, but don’t always, praise your child for completing their chores, they’ll keep up the good behavior in the hopes of receiving praise the next time.

Second, uncertain incentives are challenging, and challenge is motivating. So, for example, athletes stay motivated because of—not in spite of—the fact that victory is never assured.

Finally, uncertainty can be exciting. Think about the appeal of lotteries. Not knowing whether or not you’ll win a prize makes you excited to play. Resolving uncertainty is psychologically rewarding.

Don’t assume that if kids are always praised for finishing their homework, they’ll be more likely to do it.

Do compliment young people for a job well done, just not every time. And pick rewards out of a hat when they complete chores—the surprise prize might keep everyone motivated to get things done.

With gratitude,

Ayelet

Ayelet Fishbach, a professor at the University of Chicago Booth School of Business, is the author of Get It Done: Surprising Lessons From the Science of Motivation.