Time explores some of the cultural ideas Americans have about only children. These ideas date back to the late 1800s and are still common today.

Some of the recent research on this topic has been conducted by sociologists. Toni Falbo has countered some of the prevailing cultural ideas:

Twenty-five years ago, she and colleague Denise Polit conducted a meta-analysis of 115 studies of only children from 1925 onward that considered developmental outcomes of adjustment, character, sociability, achievement and intelligence. The studies, mainly from the U.S., cut across class and race. Generally, those studies showed that singletons aren’t measurably different from other kids — except that they, along with firstborns and people who have only one sibling, score higher in measures of intelligence and achievement. No one, Falbo says, has published research that can demonstrate any truth behind the stereotype of the only child as lonely, selfish and maladjusted.

People also have ideas about families that have too many children. Recent coverage and discussions of the Octomom and the Duggars (of 19 Kids & Counting) show there are powerful thoughts about not having too many children.

According to the article, a 2010 Pew survey showed 46% of American adults thought two children was the best number.

It’s fascinating to think that much decision-making about this is driven by economics. When families had farms and mortality rates were higher for children, families had more kids. Today, raising a child is expensive and life expectancy is higher so people have fewer kids.