An Attempted Replication of the Relationships between Birth Order and Personality

According to Sulloway (1996), firstborn children hold positions of dominance and parental favor relative to laterborn children and, as a consequence, develop personality characteristics that coincide with parental interests. Laterborns develop personality characteristics that differ from firstborns in an effort to secure parental investment. Sulloway (1996, in press) reported support for the hypotheses that firstborn status correlates positively with Surgency and Conscientiousness and correlates negatively with Agreeableness, Emotional Stability, and Openness after controlling for sex, age, sibship size, and socioeconomic status. The authors attempt to replicate these findings with self-report data provided by several hundred young adults, including a sample of full genetic siblings and a sample of mixed (half-, step-, or adoptive) siblings. For the complete sample and the full sibling sample, they replicate the negative relationship between firstborn status and Agreeableness. Contradicting Sulloway's findings, the authors document in the complete sample and in the mixed sibling sample a positive relationship between firstborn status and Openness. They find no relationships between firstborn status and Surgency, Conscientiousness, or Emotional Stability. Discussion situates the results of the current research with previous attempts to replicate Sulloway's (1996) findings.