Firstborn Kids Are Smarter, Study Says ...but their brothers and sisters get better grades By Kevin Spak, Newser Staff Posted Aug 13, 2010 10:17 AM CDT 15 comments Comments Firstborns score better on tests, but later-born kids get better grades. (Shutterstock) (Newser) – Firstborn kids are generally more intelligent than their brothers and sisters, but younger siblings do better in school and are more outgoing, according to a new study. Previous birth-order research looked at children in isolation—e.g., how many presidents are firstborns?—but the new study examined 90 pairs of siblings in high school. Researchers found that while the first -borns scored better on tests, their siblings had better grade point averages. Firstborns are assumed to have an advantage because they were at one point the sole recipient of their parents’ attention, LiveScience explains. Researchers theorize that later-borns may earn better grades thanks to help from older siblings who’ve been through the same classes, or because they feel pressure to compete with them. The researchers also asked the subjects to take a personality quiz and found that, contrary to popular belief, the younger siblings were more extroverted. Firstborns, meanwhile, have a perfectionist streak.