birth order
the ordinal position of a child in the family (first-born, second-born, youngest, etc.). There has been much psychological research into how birth order affects personal adjustment and family status, but the notion that it has strong and consistent effects on psychological outcomes is not supported. Early interest in birth order appears in the work of Francis Galton and Sigmund Freud, but it was Alfred Adler who first proposed that birth order is an important factor in personality development. Current family-structure research sees birth order not so much as a causal factor but rather as an indirect variable that follows in importance more process-oriented variables (e.g., parental discipline, sibling interaction, genetic and hormonal makeup).