Young children understand how social connections affect what people know about each other

An unwritten expectation in our everyday social interactions is that inti-mate personal information about someone—“insider knowledge”—is usuallyconfined within close relationships. For example, it would be odd, or evenunsettling, if a stranger knew about your favorite movie. Such expectationsabout who knows what about whom is a cornerstone of complex social behav-ior that reflects a rich understanding of how social connections shape whatpeople know about each other. Drawing on parental report (Study 1) as wellas a novel experimental approach using controlled but naturalistic conversa-tions (Study 2 & 3), here we demonstrate that 4- to 5-year-old children canrapidly infer who has insider knowledge about people. Children reported be-ing surprised when someone possessed personal knowledge misaligned withtheir relationships, such as a stranger knowing their favorite food or theirown parent knowing a stranger’s favorite movie. Children could also explainhow someone might have acquired that knowledge, either through first-handobservation or second-hand sources. These findings not only demonstratean early-emerging understanding of how individual minds are shaped in thecontext of their relationships and social networks, but also a remarkablyprecocious ability to deploy such understanding in real-time interactions todetect and explain anomalies in what people know about each other.