Birth-order effects on risk taking are limited to the family environment.

Why is the empirical evidence for birth-order effects on human psychology so inconsistent? In contrast to the influential view that competitive dynamics among siblings permanently shape a person's personality, we find evidence that these effects are limited to the family environment. We tested this context-specific learning hypothesis in the domain of risk taking, using two large survey datasets from Germany (SOEP, n = 19,994) and the United States (NLSCYA, n = 29,627) to examine birth-order effects on risk-taking propensity across a wide age range. Specification-curve analyses of a sample of 49,621 observations showed that birth-order effects are prevalent in children aged 10-13 years, but that they decline with age and disappear by middle adulthood. The methodological approach shows the effect is robust. We thus replicate and extend previous work in which we showed no birth-order effects on adult risk taking. We conclude that family dynamics cause birth-order effects on risk taking but that these effects fade as siblings transition out of the home.