Parents who "overvalue" children during a key developmental stage - telling them they are superior and entitled to special treatment - are more likely to produce narcissists, a new study suggests.

Ohio State University psychologist Brad Bushman and Dutch colleagues followed 565 children ages 7 to 11 from middle-class neighborhoods in the Netherlands, along with their parents - 415 mothers and 290 fathers.

Four times over 18 months, parents and children answered questionnaires designed to assess the children's self-esteem and egotism, as well as the parents' warmth and opinion of their children's specialness.

Psychoanalytic theory has long posited that narcissists were the result of parents who showed them too little warmth.

But the new research, in last week's Proceedings of the National Academy of Sciences, bolsters social learning theory - the idea that children learn through modeled behavior. Those whose parents thought they were overly special became convinced of it.

"Of course, parental overvaluation is not the sole origin of narcissism," the researchers conceded.

- The Washington Post