Parental Correlates of Child's Iq and Height: A Cross-Validation of the Berkeley Growth Study Results1

In recent years there has been increasing interest in the degree to which environmental pressures and events can influence both IQ level and IQ change during the childhood years (2, 6, 8, 9, 11). Most investigators have reported an average correlation of .50 between the IQ of the school age child and the IQ of the parent (3, 5, Io), and this finding has often been interpreted as indicating the influence of genetic mechanisms on intelligence test performance. However, the size of these correlations leaves much variance to be accounted for, and there are data to suggest that environmental variables may also influence IQ score. Eels and Davis (6) have reported positive correlations ranging from .20 to .43 between socioeconomic level and various IQ test scores. One interpretation of these correlations is that the child in a middleor upper-class home is more apt to encounter verbal stimulation and encouragement of language skills than a child from a lower class family. It is assumed that this middle class emphasis on language development facilitates IQ score. Kagan and Moss (8) have found that parental attitudes do influence early IQ, for ratings of maternal concern with intellectual development were positively correlated with the IQ of the 3-year-old child when maternal IQ was held constant. However, the controversy over whether IQ is determined by nature or nurture seems less intense now than it was a decade ago. Psychologists are beginning to address themselves to a more plausible question: namely, to what degree and in what ways do genetic and environmental variables influence IQ score.