Birth-Order Differences in Special Ability: Fact or Artifact?

Abstract

A 1% subsample of Project Talent Data Bank's national high school sample provided test score and demographic data for 3,308 Ss. Partial correlation and multiple regression methods were used to test hypotheses concerning birth-order differences in special ability, over and above expected differences due to sex or to socio-economic status. After controlling for socio-economic status and family size, birth order accounted for only 2% of the variance in Vocabulary and English test scores; and birth order accounted for less than 1% of the variance in the Mechanical Reasoning, Visualization, Arithmetic Computation, Clerical Checking, and Object Inspection scores. Sex differences in ability were independent of birth order and socio-economic status.