A study has found that first-born children tend to score slightly higher on IQ tests than their younger siblings, adding fresh evidence to the long-debated 'birth order' theory. Published in the Proceedings of the National Academy of Sciences (PNAS), the research found a small but consistent drop in cognitive scores with each birth-order position. Researchers also noted that birth order had little to no effect on personality traits such as extraversion or agreeableness, despite long-running stereotypes about sibling roles. 📸 Getty #research #science #IQ #intelligence