Sibling Influence on Smoking Behavior: A Within‐Family Look at Explanations for a Birth‐Order Effect

Using a repeated‐measures design, we found a significant birth‐order relationship suggesting lower ages of smoking onset in later born siblings of a 1979 National Longitudinal Survey of Youth cohort. Two social learning mechanisms, modeling and opportunity, were explored to help illuminate the causes of trends in the within‐family means. When empirical patterns were compared to predictions derived from our specifications of how opportunity and modeling processes should work, the results were unsuccessful in explaining the birth‐order effect. As a third explanation of the birth‐order effect, telescoping did show a significant influence. The effect size was small, however, and had little effect on the group means assessed. Finally, a pattern did emerge that was consistent with a reformulation of the opportunity process in which sisters play a particularly strong role. We develop future research implications of this pattern and speculate on genetic and social conservatism explanations.