If you want someone to stop asking you for money, the worst thing you can do is say no and then give in after persistent pleading.

Such “intermittent reinforcement” — granting a reward after an unpredictable number of requests — makes it more likely the person will ask for another handout than if you just said yes at the start, says Brad Klontz, a certified financial planner and psychologist in Lihue, Hawaii, who researches financial psychology. It’s the same dynamic that lures people to slot machines and lotteries.

Klontz doesn’t actually advise giving in. But he says understanding the psychology on both sides of what he calls “financial enabling” can help people change their behavior.

In my latest for the Associated Press, how to stop financially enabling your family.