Biological nonoptimality and quality of postnatal environment as codeterminants of intellectual development.

The relation of nonoptimal condition at birth to the intellectual development of children reared in 2 different environments was investigated in a 4 1/2-year longitudinal experiment. Subjects were 80 disadvantaged children, half of whom were randomly assigned at birth to a day-care program designed to prevent mild mental retardation and half to an educationally untreated control group. All subjects for this report were full-term and weighed over 2,500 grams at birth; condition at birth was considered nonoptimal if the 1-min Apgar score was less than or equal to 8. Results indicated that nonoptimal perinatal status had significant adverse effects on 4 1/2-year scores on the McCarthy Scales of Children's Abilities in the control group (p less than .01); however, test scores of children with optimal or nonoptimal Apgars did not differ within the group that received educational treatment. The results provide support for a framework stressing initial biological vulnerability and subsequent environmental insufficiency as cumulative risk factors in the development of children from low SES families.