The influence of low family income from birth to adolescence and adulthood on intelligence: Findings from two Brazilian birth cohorts

Research to date on the impact of income throughout the life course on intelligence is inconclusive due to limited evidence. We set out to examine whether two models of life course family income (family income trajectories and low family income at birth) predicted a lower subsequent intelligence quotient (IQ). Data from two Brazilian birth cohorts were used (1993 and 1982 Pelotas Birth Cohorts). In both cohorts, a clear gradient was observed in distribution of IQ scores by family income trajectories across the life course. Participants in the Stable low-income group had the lowest IQ scores. Low family income at birth had a direct negative effect on subsequent IQ in the 1993 and 1982 cohorts. Our findings provide new insights about the relationship between low family income and IQ in adolescence and adulthood.