#BehavioralGenetics

In identical Bangkok apartments and rural Thai households throughout the kingdom, brothers and sisters grow up sharing the same parents, bedrooms, and dinner tables yet emerge with childhood memories so fundamentally different they could have been raised in entirely separate families—one sibling recalling warmth, encouragement, and family stability while another remembers criticism, unfair treatment, and emotional neglect that profoundly shapes their adult relationships and mental health. This puzzling phenomenon affecting millions of Thai families across all social classes represents far more than simple childhood forgetfulness or selective memory, according to revolutionary behavioral genetics research that has transformed scientific understanding of how family environments actually influence individual development throughout childhood and beyond.

In a shift from the long-held belief that parenting is the primary force in determining a child’s outcomes, a growing body of research indicates that siblings may play an equally significant—if not greater—role in molding each other’s personalities, achievements, and life trajectories. This fresh perspective, featured in the latest cover story of The New York Times Magazine, draws on a range of recent studies examining the “sibling spillover effect,” and is prompting both researchers and families globally, including those in Thailand, to reconsider just how children influence one another within the family unit (NYTimes).