BACKGROUND: Although research into the continuity and change of personality traits during a lifespan has been fairly extensive, little research has been conducted on childhood predictors of adult personality.

PURPOSE: We aimed to investigate the association between infant socioeconomic status (SES), and Eysenck personality traits in adulthood. An additional aim was to investigate whether intelligence and education may mediate this association.

METHODS: SES of 9125 children in the Copenhagen Perinatal Cohort was recorded at a 1-year examination. A subsample of this cohort, comprising 1182 individuals, participated in a follow-up at 20-34 years and was administered the Eysenck Personality Questionnaire (EPQ) which includes measures of neuroticism, extraversion, psychoticism and the so-called lie-scale. Associations of SES with each of the four personality traits were analysed by bivariate and partial correlations, and the mediating effects of intelligence and years of education were analysed.

RESULTS: Higher SES in infancy was associated with lower neuroticism (r = -0.06; p = 0.05), lower lie-scale scores (r = -0.11; p = 0.0002), and higher psychoticism (r = 0.09; p = 0.003). However, analyses of mediation revealed no direct effect of infant SES on any of the adult personality traits, but only indirect effects mediated by intelligence and years of education, with intelligence being the main mediating factor.

CONCLUSION: Only weak associations were observed between infant SES and personality in young adulthood, and the observed associations were mediated by adult intelligence and educational level. Thus, factors associated with infant SES or family background appears to have weak direct effects on personality development.