Analysing effects of birth order on intelligence, educational attainment, big five and risk aversion in an Indonesian sample

Few studies have examined birth order effects on personality in countries that are not Western, educated, industrialized, rich, and democratic (WEIRD). However, theories have generally suggested that interculturally universal family dynamics are the mechanism behind birth order effects, and prominent theories such as resource dilution would predict even stronger linear effects in poorer countries. Here, we examine a subset of up to 11188 participants in the Indonesian Family Life Survey to investigate whether later-borns differ from earlier-borns in intelligence, educational attainment, Big Five, and risk aversion. Analyses were performed using within-family designs in mixed-effects models. In model comparisons, we tested for linear and non-linear birth order effects as well as for possible interactions of birth order and sibship size. Our estimated effect sizes are consistent with the emerging account of birth order as having relatively little impact on intelligence, Big Five, and risk aversion. We found a non-linear pattern for educational attainment that was not robust to imputation of missing data and not aligned with trends in WEIRD countries. Overall, the small birth order effects reported in other studies appear to be culturally specific.