You've probably heard that first-born siblings are bossy, or natural leaders, and over ambitious. A lot of that might be folklore, but a 2017 study found that some of the birth order stereotypes may hold true. "As early as age one, latter-born children score lower on cognitive assessments than their siblings, and the birth order gap in cognitive assessment increases until the time of school entry and remains statistically significant thereafter," according to the study published in Journal of Human Resources. Translation: The oldest siblings really are the smartest.
For the study, researchers analyzed data collected from about 5,000 children up to 14 years old. They also talked to parents about their behavior during pregnancy and afterwards. As the Miami Herald explains: "The findings showed first-born children tended to score higher on verbal, reading, math and comprehension skills as early as just after birth to age 3, and differences in performance between first-borns and other children increased with age."