The relation of severe malnutrition in infancy to the intelligence of school children with differing life histories

Abstract

The IQ's of Jamaican boys aged 6-10 were associated significantly with the presence or absence of severe malnutrition in infancy, with height at time of IQ testing, and with a measure of the boys' social background. A multiple correlation coefficient of 0.674 was obtained between IQ and the three factors. Social background contributed 0.294 of the variance, height 0.112, and severe malnutrition 0.049. The two extreme groups of boys, i.e., those malnourished, small at follow up, and with unfavorable social backgrounds and those not malnourished, tall at follow up, and with favorable social backgrounds had average IQ's of 49.4 and 74.9, respectively. Only two of the boys in the most advantaged group had IQ scores that overlapped with the most disadvantaged group. Boys with severe malnutrition in infancy, but who are tall at follow up and have a favorable social background have an average IQ 11 points higher than boys who did not experience severe malnutrition, but who are short at follow up and have an unfavorable social background. The difference in IQ between boys who did and did not experience severe malnutrition in infancy varies under different conditions of height and social background when those are held constant for both groups. Under the most favorable conditions of being tall and having an advantageous social history the average IQ of the malnourished boys is only 2 points lower than those not malnourished. Under the most unfavorable conditions of short stature and a disadvantageous social background the IQ of the malnourished boys is 9 points lower than those not malnourished.