Birth order and risk taking in athletics: a meta-analysis and study of major league baseball.

According to expectations derived from evolutionary theory, younger siblings are more likely than older siblings to participate in high-risk activities. The authors test this hypothesis by conducting a meta-analysis of 24 previous studies involving birth order and participation in dangerous sports. The odds of laterborns engaging in such activities were 1.48 times greater than for firstborns (N = 8,340). The authors also analyze performance data on 700 brothers who played major league baseball. Consistent with their greater expected propensity for risk taking, younger brothers were 10.6 times more likely to attempt the high-risk activity of base stealing and 3.2 times more likely to steal bases successfully (odds ratios). In addition, younger brothers were significantly superior to older brothers in overall batting success, including two measures associated with risk taking. As expected, significant heterogeneity among various performance measures for major league baseball players indicated that older and younger brothers excelled in different aspects of the game.