You may have heard that first-born children are more intelligent and successful than their younger siblings, but not because they used up all the “good genes” from their parents. Rather, a new study from the University of Edinburgh found that eldest children’s greater intelligence may be a result of the extra attention they receive from their parents, something their younger siblings aren’t as lucky to receive.

According to the research, evidence of first-born children’s increased intelligence can be seen as early as their first birthday. This increased intelligence may be due to the extra mental stimulation firstborns receive in their early days, The Independent reported. Although all children seemed to receive the same amount of emotional support from their parents, regardless of birth order, parents spent less time on brain-stimulating activities with younger children. As a result, younger siblings did fewer creative activities and were exposed to fewer books and music, the report suggests. This may have affected their intellectual potential.

Read: The Birth Order Effect: How Siblings May Influence Personality Traits In A Family

For the study, the researchers examined data from 5,000 children who were given reading and picture vocabulary tests every two years. Increased intelligence was noted at around the one-year mark, increasing each year until 14.

While the results are interesting, the team emphasized that these findings are more of a generalization and won't apply to every family situation, the Independent reported. In fact, other research has suggested that the correlation between birth order and intelligence is highly overrated. For example, a 2015 study looked at the personality and intelligence of 377,000 high school students — the largest pool to ever be studied for the outcomes of birth order, and found that differences were insignificant.

For example, although first-born children did tend to be more intelligent than their younger siblings, this was often only by one point. The same was true with personality differences. The report found that although first-born kids tended to be more extroverted, agreeable, conscientious, and have less anxiety than their younger siblings, this difference was “infinitesimally small.”

It’s not all good news for the first borns. Along with increased intelligence, first-born children may also be more likely to be overweight. A small study of middle-aged men in New Zealand found first-born children to weigh about 14 pounds more, with larger measures of body mass index than second-born siblings. However, the study was small and this trend doesn't mean first-born children are destined to a future of obesity.

Source: Lehmann JYK, Nuevo-Chiquero A, Vidal-Fernández M. The Early Origins of Birth Order Differences in Children’s Outcomes and Parental Behavior. Journal of Human Resources. 2017

See Also:

Firstborns More Likely To Be Overweight

Birth Order May Predict Intelligence And Illness In First-Borns, But Vitality In Their Siblings