The purpose of this article is to demonstrate the value of examining a
variety of pressing behavioral, medical, and social phenomena as they
relate to gradations in general intelligence. Although few (if any) v
ariables in the social sciences can compete with the construct of gene
ral intelligence in its ability to forecast an array of socially value
d attributes and outcomes, measures of general intelligence are seldom
incorporated into correlational and experimental designs aimed at und
erstanding maladaptive behavior (e.g., crime, dropping out of high sch
ool, unwise financial planning, health-risk behaviors, poor parenting,
and vocational discord) or its opposite, highly adaptive behavior. We
contend that, if consulted more often, the construct of general intel
ligence would contribute to understanding many puzzling human phenomen
a, because successive gradations of intelligence reflect successive de
grees of risk. A method is provided for uncovering group trends, one e
xpressly designed to reveal the range and prevalence of the many diffe
rent kinds of human phenomena that vary as a function of intellectual
gradations. By employing this method, policymakers and the public can
more readily apprehend the significant, but often unsuspected, contrib
ution made by general intelligence to many socially important outcomes
. Our approach is similar to traditional epidemiological research aime
d at ascertaining antecedents to maladies through the defining feature
s of high-risk groups (e.g., for lung cancer, smokers and passive smok
ers; for AIDS victims, participants in unsafe sex; for academic medioc
rity, among the intellectually gifted in nonaccelerative educational t
racks; for mental retardation, high blood-lead levels). Once Such high
-risk groups are defined (i.e., groups of persons whose behavioral dis
positions predispose them, and often others around them, to unfortunat
e outcomes), policymakers and scientists are in a better position to d
isentangle genuine causes from families of correlations and can concen
trate ameliorative resources more effectively. Data from educational a
nd medical contexts are analyzed to show how measures of general intel
ligence, and other dimensions from differential psychology, can comple
ment epidemiological and social science inquiry. We also argue that by
incorporating such measures of human variation into policy developmen
t and research, policymakers are more likely to forestall ''iatrogenic
effects'' (maladies caused by treatment).