influential accounts of the motivations for homicide. The
sex difference in the commission of violent crimes—
including homicide—was one of the first and most obvi-
ous observations demanding explanation. Men are more
often than women both the offenders and the victims of
homicides. Socialization theories argue that men, more
than women, have been socialized to view aggression as
a permissible means to achieve certain ends. This differ-
ential socialization for aggressive behavior in men and
women, it is argued, can explain the greater homicide
rates among men. While this theory has been well
received within psychology, there is growing evidence
that an exclusive reliance on this theoretical position to
explain homicide patterns leads to incomplete conclu-
sions. Socialization theories push back one step many of
the most intriguing questions psychologists working to
understand homicide have tried to answer. Why are men
and women differentially socialized to behave aggres-
sively? Why are boys and girls differentially receptive to
certain aspects of environmental input? Socialization
theories cannot provide answers to such questions.
Despite the limitations of environmental theories, insight
has been gained from the research conducted by social
scientists focusing on social and cultural influences. One
notable finding reflecting the cultural and demographic
variables within cultures has resulted from research on
homicide rates across the United States.
Social scientists have identified key sociocultural
beliefs and attitudes that vary by region and have ana-
lyzed homicide rates as a function of these different
beliefs and attitudes. The Southern states in the United
States adhere more strongly to a “culture of honor”
than other regions. In the Southern states, men act
more aggressively than men in the Northern states to
protect their honor and their reputation. This differ-
ence is arguably generated by exposure to a culture in
which honor and reputation are very important in pro-
tecting resources. Of the state executions that have
occurred since 1977, 82% have occurred in the
Southern region of the United States. In addition to
these social explanations of homicide, recent break-
throughs have been made in understanding the biolog-
ical roots of homicide.Biological Theories
Advances in technology now provide researchers
with an unprecedented window into the brain activ-
ity of murderers. These technological advance-
ments include functional magnetic resonance imaging,electroencephalography, computed tomography, and
positron emission tomography, all of which can be
used to study neurological and neuroanatomical
abnormalities in the brains of individuals who have
perpetrated homicide. Research has shown distinct
neurological activity in individuals who have homici-
dal thoughts or who exhibit violent behaviors.
One perspective explicit in the call for integration
of biological (e.g., genetic predispositions), psycho-
logical (e.g., psychological disorders), and social
(e.g., poverty) explanations of homicide has been
aptly named the biopsychosocial perspective. There
are limitations to this theory because many of the bidi-
rectional relationships between these three metafac-
tors have not yet been fully explored. Although this is
a promising theoretical position, a wealth of new
research is yet to be conducted exploring the links
between these factors. Inherited predispositions for
particular personality disorders may influence how an
individual is perceived and treated by others. The way
an individual is perceived and treated by others pro-
vides a feedback loop, altering cognitions about rela-
tionships with others that can influence personality. In
sum, there are numerous potential pathways to homi-
cide, and we will be better positioned to expand on
these interrelationships with future research.
In many of the cases, links between abnormal cog-
nition and brain activity have been documented.
Murderers have been diagnosed with psychological
disorders such as antisocial personality disorder or
other personality disturbances, psychological stres-
sors, various types of childhood trauma, and drug and
alcohol abuse problems. Not all these psychological
disorders, however, apply to all killers. Many known
factors combine to result in individual differences in
brain patterns and cognition and complicate our under-
standing of the psychology of homicide. We believe
that insight gained from various areas of the psycho-
logical and other behavioral sciences will provide
greater clarity into the motivations and development of
homicidal thoughts and behavior. Various theories
have recently shed light on homicidal psychology in
ways that have previously escaped psychologists.Evolutionary Perspectives
One particularly powerful theoretical perspective that
has yielded insight has been the application of evolution-
ary perspectives to the study of homicide. An evolution-
ary psychological approach to homicide is relatively newHomicide, Psychology of——— 357H-Cutler (Encyc)-45463.qxd 11/18/2007 12:43 PM Page 357