A multilevel approach to the relationship between birth order and intelligence.
Many studies show relationships between birth order and intelligence but use cross-sectional designs or manifest other threats to internal validity. Multilevel analyses with a control variable show that when these threats are removed, two major results emerge: (a) birth order has no significant influence on children's intelligence and (b) earlier reported birth order effects on intelligence are attributable to factors that vary between, not within, families. Analyses on 7- to 8 - and 13- to 14-year-old children from the National Longitudinal Survey of Youth support these conclusions. When hierarchical data structures, age variance of children, and within-family versus between-family variance sources are taken into account, previous research is seen in a new light.
Wichman
Aaron L
AL
Department of Psychology, The Ohio State University, USA.
Rodgers
Joseph Lee
JL
MacCallum
Robert C
RC
D000293:Adolescent; D001722:Birth Order; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007360:Intelligence; D008297:Male; D008960:Models, Psychological