The relationship between nutritional status, measured by height for age, and cognition, measured by WISC full-scale IQ, was studied in a longitudinal sample of 459 urban Guatemalan children, aged 4-9 years, from a disadvantage community of the fringe of Guatemala City, examined annually over a 3 year period. Socioeconomic status (SES) was controlled by developing a composite index for each home. The mean IQ differed significantly from the lowest to the highest quartiles of stature, the difference between the two extreme quartiles being approximately 0.3 SD of IQ. There was a significant interaction between SES and stature in their effects on IQ. Whereas nutritional status and SES affected IQ in an additive fashion in the upper three SES quartiles, there was no difference in IQ attributible to stature among children from the most disadvantaged homes. This analysis indicates that the mild-to-moderate protein-energy malnutrition (defined by height for age) that is prevalent among children from disadvantaged environments in developing countries is significantly related to cognitive development. However, in the poorest homes, SES is seen as a more important determinant of cognitive development than stature.

Longitudinal data from a study of child development in Guatemala City were used to describe the influence of socioeconomic status and sex on physical and cognitive growth status. The correlation between the growth status variables was also analyzed. The sample included 144 Guatemalan children, 46 of low SES, 52 of middle SES, and 46 of high SES. The children were students in 5 urban primary schools. 3 physical variables, height, weight, and skeletal age, were measured annually from first to sixth grade. Two cognitive variables, general intelligence and reading ability, were measured in grades 1, 3, 4, or 5. Significant differences between SES groups existed for all variables. However, the differences in each grade were greater for the cognitive measures than for the physical measures. Compared with high SES children, middle SES boys and low SES boys and girls experienced significantly greater delayed growth in height than in weight or skeletal age. It is possible that these height delays may result in a permanent reduction in stature. The only consistently significant sex-related difference was for skeletal age; girls were more mature than boys in each grade. When SES was statistically controlled, there was no significant correlation between physical and cognitive growth status for girls and only a few moderate but statistically significant correlations for boys.

The rate of growth in height and the timing of adolescent growth events are analyzed for two samples of Guatemalan children. One sample includes Mayan school children, 33 boys and 12 girls between the ages of 5.00 to 17.99 years, living under poor conditions for growth and development. The second sample includes ladino children, 78 boys and 85 girls of the same age range, living under favorable conditions for growth. The Preece-Baines model I function is used to estimate mean values for rates and timing of childhood and adolescent growth events for the two groups. Significant statistical contrasts (t-tests) of these means show Mayan boys reach the age of "take-off" (TO; the onset of the adolescent growth spurt) 1.45 years later, achieve peak height velocity (PHV) 1.68 years later, and continue growing for about 2.0 years longer than do the ladino boys. Despite the Mayan boys' increased duration for growth they grow significantly more slowly than the ladinos. Mayan boys are 6.60 cm shorter than ladinos at the age of TO and are estimated to be 7.71 cm shorter than the ladinos at adulthood. Mayan girls reach the age of TO 0.93 years later than do the ladina girls, but the two groups do not differ in the age at PHV or the age at adulthood. The mean height of Mayan girls is significantly less than that of ladinas at the age of TO (6.5 cm), and this difference increases to an estimated 11.14 cm at adulthood. Possible causes of these ethnic and sex-related differences in amounts and rates of growth are discussed in relation to hypotheses about the genetic and environmental determinants of human development.

The Preece-Baines model I function, adapted for use with a personal computer, is applied to the longitudinal growth records of Guatemalan children and adolescents of high socioeconomic status. The fit of the Preece-Baines function to the Guatemalan data is compared with those of published analyses of the function fitted to the growth of British, Belgian, urban and rural Indian, Australian Aborigine, and African children. Guatemalan, British, and Belgian samples share generally favorable environments for human development and show few differences in the amount and velocity of growth, or in the timing of growth events. Urban Indians live under relatively good environmental conditions and are similar to Guatemalans in the timing of growth events, but grow more slowly and grow less than the Guatemalans, British, or Belgians. Rural Indian, Australian, and African samples live in environments that delay or retard growth, and these last-named three samples grow more slowly, delay the onset of the adolescent growth spurt, and achieve smaller adult height than the Guatemalans. Parameters of the Preece-Baines model are compared between all samples and show that there are several alternate paths in the rate of growth and the timing of adolescent growth events that may be taken from childhood to adulthood.

The effects of hereditary and environmental factors upon the growth in stature of children living in Guatemala City has been studied. Heights at yearly examinations were fitted, by individual, to a double logistic curve in samples of Guatemalan and European children attending a private school in Guatemala City. These two samples differed genetically yet shared the same environment. Their growth was compared, by a multivariate analysis of the parameterized curves, to that of children from the Berkeley Growth Study, genetically similar to the European sample, yet living in different environments. The European children in Guatemala grew, before adolescence, more similar to Guatemalan and differed significantly from the Berkeley sample children. However, the amount of growth during the adolescent years experienced by the European children was similar to that of the Berkeley sample and differed from their Guatemalan counterparts.