Contrary to the presumption that only children are more selfish than children raised in larger families, Fehr found the onlies to be the more cooperative and selfless. They were completely untroubled by handing over toys to another child, whereas the siblings flatly refused. Fehr came to the conclusion that the onlies didn’t know to be competitive because they’d never had to compete…They weren’t afraid of sharing toys, because they didn’t understand if you gave Barbie to another child, she might come back missing her leg or head.
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If people actually spent time with only children, they would know how unrealistic the the conventional wisdom is.