Do Human Figure Drawing IQ Scores Match Wechsler IQ Scores? A Reared-Apart Twin Study

Agreement between IQ scores derived from human figure drawing tests and standard general intelligence tests has been of interest to psychological investigators and practitioners. Some early studies found associations between drawing performance and motor skills, but few recent investigations have detected meaningful relationships with cognitive ability. Furthermore, few twin studies have considered a genetic component to scores on drawing tests. The present study is the first to undertake these analyses using adult reared-apart twins. Both drawing-derived IQ scores and Wechsler IQ scores were available for reared-apart monozygotic (MZA, N = 71) twin pairs and reared-apart dizygotic (DZA: N = 53) twin pairs from the Minnesota Study of Twins Reared Apart (MISTRA). Intraclass correlations for the drawing-derived performance scores were modest, but significantly higher for MZA (r_i = .31, p < .01) than DZA twin pairs (r_i = .02, ns), p < .001. Intraclass correlations for the Draw-a-Person IQ score (DAP:IQ) showed the same pattern. Finally, the correlation between the drawing-derived IQ scores and Wechsler IQ scores was quite small with a low effect size, but statistically significant (r = .15, p = .02). These findings suggest modest genetic influence on drawing performance. Like most previous studies of nontwins, little meaningful or practical association between the two IQ measures was indicated.