Here’s my Q&A column from the WSJ this week — and if you have any questions for me, you can tweet them to @danariely with the hashtag #askariely, post a comment on my Ask Ariely Facebook page, or email them to [email protected].

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Dear Dan,

I’m raising two teenagers and have discovered just how hard it is to teach them to be polite, to clean up after themselves and to leave the house on time. Would it make sense for me to pay them for better behavior?

—Billy 

Simple rewards may seem like a good idea, but they often have unintended consequences. Consider the case of Kelly the dolphin, who lived in a marine institute in Mississippi. To teach her to keep her pool clean, her trainers started trading her fish for any litter she collected.

Kelly soon learned that litter of any size would win her a treat. So when a visitor dropped paper into the pool, she would hide it under a rock and tear off one piece at a time to get more fish. Her response was logical but not exactly desirable.

Something similar can happen with children. In studies conducted in the 1980s, psychologist Barry Schwartz had a teacher pay children for every book they finished. The children started choosing shorter books with large print in order to get more rewards—and they reported liking reading less. I think it’s best to teach your children how to act, not how to maximize their pay.

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Dear Dan,

I recently bought a DNA test to learn about my ancestors’ roots. The test had an option to let me find out if I carry DNA mutations that increase the chances of Parkinson’s, Alzheimer’s and other diseases. I chose to include those tests, but now I can’t help feeling anxious about getting the results. What would you have done?

—Natalia 

Genetic information is becoming more and more available, for good and ill. Though medications exist for the diseases you mention, scientists think that Parkinson’s and most Alzheimer’s cases are not preventable, so if I were you, I would stick my head in the virtual sand and not find out about the DNA mutations. A bad result would cause you needless stress and might weaken your immune system.

We all stand a chance of getting these diseases, and the best way to deal with that prospect is to take better care of our bodies and minds in preparation for old age. We also should be kinder to our significant others and children, because they’re likely to be our eventual caretakers.

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Dear Dan,

The state of the world is depressing me. It feels that whatever good I do is a small drop in the bucket compared with a daily flood of illogical, ignorant and evil actions. How can I keep going and find hope?

—Stacy 

Over the past few years I’ve spent time with people who had suffered very complex injuries and were trying to regain their drive and sense of purpose. One thing they did was to set achievable goals and measure their progress toward them—the classic idea of “light at the end of the tunnel.” If you can focus on positive changes that you can make in the near term, it should help your motivation—and make you happier. Good luck.

See the original article in the Wall Street Journal.