How Similar are Siblings? What Makes Us Different?

It’s obvious to many of us — whether we’re an only child or not — that siblings are often different from each other. Judy Dunn, emeritus professor of developmental psychology at Kings College London, and Robert Plomin, professor of behavioral genetics at the same institution, were among the first scholars to start empirically questioning why this happens. Drawing from differences they noticed in Dunn’s children, over the past 30 years, they’ve tested siblings&