reports—replete as they are with accounts of domes-
tic violence, aggravated assault, murder, and rape
under its influence. Substance abuse has a particularly
deleterious effect on individuals with preexisting
mental disorder, exacerbating their dysfunction. It is
not that alcohol causes violent behavior; rather, it
appears to trigger violence in those already prone to
behave violently by virtue of other factors.
Exposure to toxic agents in the environment such as
pesticides and lead can delay or impair an individual’s
intellectual development and thus affect behavior and
its regulation. In this regard, teratogens—factors that
interfere with normal embryonic development—have a
particularly important role in predisposing some indi-
viduals to a life of crime. The legacy of cognitive
deficits and behavioral sequelae due to, for example,
prenatal exposure to drugs and alcohol, are well docu-
mented in the literature.
Neurotransmitters are responsible for conducting
electrochemical impulses within and across regions of
the brain (as well as throughout the body). Many psy-
chiatric disorders have been linked to imbalances in
neurotransmitter systems. Serotonin is involved in a
number of brain functions, including regulation of
emotional states. In laboratory experiments, lowering
the serotonin levels results in the onset of impulsive
and aggressive behavior. That abuse and neglect in
childhood can result in permanently reduced levels of
serotonin is therefore an important observation for our
understanding of the etiology of violence.
Hormones function in much the same way as neu-
rotransmitters except they are released into the blood-
stream rather than between neurons. Abnormally high
levels of circulating testosterone—a sex hormone
associated with the drive to dominate and compete—
have been linked to excessive aggression. The phe-
nomenon of “roid rage” in body builders who use
anabolic steroids and exhibit extreme and uncontrol-
lable violence attests to this effect. Such observations,
as well as research on stress hormones correlating, for
example, low levels of salivary cortisol with severe
and persistent aggression, show the importance of
hormonal contributions to criminal behavior.
Research on skin conductance, heart rate, and
brainwave activity has linked low arousal to criminal
behavior. In fact, in young children, these psy-
chophysiological conditions have been reported to
portend later delinquency with a high degree of accu-
racy. What these and the aforementioned studies sug-
gest is that the brains of chronic offenders workdifferently. As we proceed to identify more of the
factors linked to criminal behavior, we will take with us
one particular question, the answer to which will have
implications that at once generate fear and optimism:
To what extent are the factors genetically determined?
A variety of methodologies—examining twins and
adoptees, chromosomal abnormalities, and DNA
polymorphisms—have been applied to evaluate the
role of genetic factors in criminal behavior and aggres-
sion. Although it is not anticipated that a “crime gene”
will ever be discovered, it is clear there are genes that
code for specific neurochemicals linked to different
kinds of behavior. To illustrate, a specific—albeit
rare—mutation has been identified in a gene that holds
the recipe for a particular enzyme known to affect the
level of certain neurotransmitters in the brain. This
defect has been linked to a propensity toward impul-
sive and excessive aggression and violence in each of
the men of the family who has this mutation.
Studies in behavioral genetics support the con-
tention that aggressive behavior is moderately herita-
ble. Aggressive behaviors confer advantage to the
males of a species as they compete for territory and
access to females. Evolutionary psychology holds that
aggressive traits that increase reproductive success
will be selected and carried across successive genera-
tions. Primatologist Ronald Nadler contends that sex-
ual aggression is inherent in the behavioral repertoires
of great apes—animals that are among our closest bio-
logical affiliates. Human males, as a function of their
drive to procreate, would be naturally inclined to have
sex with as many different partners as possible, maxi-
mizing the probability that the species will survive
and also that their own genes will be transmitted to the
next generation. The fact that most males do not rape
is in large measure due to their socialization; rapists
are males who have not been effectively socialized in
this regard. We can appreciate through this example
how specific psychosocial risk factors (e.g., low intel-
ligence) can increase the probability of criminal and
violent behavior—in this case, rape.
The long tradition of assuming crime to be the
product of volition, unencumbered by aberrant psy-
chological or biological processes, is under attack. In
the end, we may find it is psychologist Adrian Raine’s
bold conceptualization of criminality as a clinical dis-
order that best fits what we learn. To embrace this
position, however, would require us to revisit our
notions of crime and punishment—and treatment. If
criminal behavior, at least impulsive violent criminal156 ———Criminal Behavior, Theories ofC-Cutler (Encyc)-45463.qxd 11/18/2007 12:41 PM Page 156