Most moms and dads swear they don’t play favorites with their kids. But a study in the journal Child Development shows that most parents DO have a favorite – giving more positive feedback to one child and more negative feedback to the other kids in the family – whether they realize it or not.

The official psychological name is “differential parenting.” And as you might expect, it’s hard on the kids who aren’t at the top of the list. But experts say it does just as much damage – or more – to the mental health of the favorite.

Here are the facts: UC Davis researchers followed 400 families. The researchers concluded that about 70 percent of the parents showed favoritism. And the researchers said that percentage is a lowball, since most parents try to hide their preference. The result? All of the children in differential-parenting families had more trouble in school and on the playground. And in some cases, the child with the most problems was the favorite.

Why would that happen? Well, even though being the favorite boosts a child’s confidence and self-esteem – it can also make kids arrogant and entitled. And those traits that don’t go sit well with others. The favorite kid can also crash and burn in the real world when they’re not being lavished with love and praise they get at home. And the unfavored kid may grow up feeling unworthy. But, they do a better job of forging friendships and relationships outside of the family as a result of that.

So, are kids aware of parental favoritism? Yes. When asked by researchers ‘who’s the family favorite’ – almost all kids knew. And it’s usually the oldest. Which is one reason they tend to have a 3-point IQ advantage over younger siblings because they get more parental attention.

What do you think: Did your parents play favorites? Did it have any impact on your adult life?