Nonparametric smoothed plot of full-scale IQ vs. dentin lead from Needleman et al. (1979). After controlling by regression for age, maternal IQ, maternal age, mother's and father's education, mother's and father's SES, number of siblings and hospitalization for lead poisoning. None of subjects excluded in original analysis were excluded from reanalysis. Source: Schwartz, in press. Reprinted with permission from NeuroToxicology; copyright 1992, Intox Press.