Prediction of Schoolage Intelligence from Infant Tests

Abstract

Fifty-eight children selected for normalcy by medical, social, and developmental criteria were tested between the ages of 3 and 33 weeks. For each infant we obtained (a) Cattell IQ scores, (b) Gesell DQ scores, and (c) a "clinical appraisal" based on total test performance. These subjects were again tested between the ages of 6 years, 2 months, and 9 years, 3 months, at that time receiving the Wechsler Intelligence Scale for Children (WISC). On theoretical grounds, and in view of previous findings, parametric measures of correspondence between infant scores and later intelligence test scores were not expected to yield significant values. In this respect, results confirmed our anticipation. The hypothesis under investigation was that, in the absence of major environmental variation, infant tests will predict the general level of later intelligence functioning within the average and superior ranges. Further, we compared the relative predictive powder in terms of intelligence ranges of Cattell IQs, Gesell DQs, and a clinical appraisal of both test protocols in combination. It proved that, when infant tests were administered to subjects younger than 20 weeks of age, no method of appraisal predicted later intelligence range. For subjects tested between 20 and 32 weeks of age inclusive, both the Cattell IQ and the Gesell DQ bore a positive relationship to later intelligence level, as assessed through a one-way analysis of variance by ranks. However, this relationship exceeds chance at the .10 level and is therefore of limited predictive value. When the same test is applied to subjects tested at 20 weeks and above but ranked on the basis of clinical appraisal, infant assessment significantly predicted differences in later intelligence range (.01>p>.01). When infant assessments were examined for their ability to distinguish merely between subjects who would later be of average or of above average intelligence, clinical appraisal (but neither of the test scores) achieved this discrimination at a highly significant level (.002). Infant tests administered under optimal conditions at 20 weeks of age and above can approximate the prediction of later intelligence range if environmental conditions are relatively stable and benign. It was further concluded that, for children in this age range, a clinical appraisal based on total test performance on 2 test instruments is a better predictor of later intelligence range than are scores obtained from either the Cattell or the Gesell tests alone. Research dealing with the contribution of biological and maturational factors to the development of later intelligence may become more rewarding once it it assumed that developmental examinations are not tests of intelligence. If infant tests are viewed as assessing only one among several determinants of intelligence, their usefulness for research purposes is not determined by the usual criteria of test validation, and the failure to predict later IQ scores does not relegate infant testing to the limbo of useless enterprises.