Affective and predatory violence: A bimodal classification system of human aggression and violence.

Research on aggression and violence has been ongoing since the mid-1920s. Early observational data in humans and animals led researchers on a quest for neuroanatomical and neurochemical substrates of such behavior. Even in these early studies, clear distinctions were made between modes of aggression. Further research confirmed multiple modes of violence corresponding to specific biogenic and psychogenic substrates.

The physiological sites critical for eliciting and inhibiting both predatory and affective aggression have been well established in animals. The afferent and efferent connections for the expression and regulation of these behaviors have been identified, along with the corresponding physical manifestations of these distinct behaviors. In addition, information regarding corresponding neurochemical systems involved in the production and modulation of these behaviors has slowly been revealed.

The application of these findings to the pathological human condition is precarious, but it has yielded prolific avenues of research and promising results. Although it is difficult to match the level of rigor and sophistication seen in the animal literature to the study of human aggression, several constructs have been researched involving human subjects. The study of natural disease processes that inflict damage on the limbic system has allowed a window of observation on and comparison to neuroanatomical substrates already demonstrated in animal models. Studies of the role of specific neurotransmitter systems have been useful in understanding not only chemical contributions but also avenues to treat and attenuate aggression in humans. Both anatomical and neurochemical studies support at least a bimodal, predatory and affective, classification system of aggression, which corresponds to unique physiological substrates and phenotypic expression. Although this bimodal classification system describes distinct forms of aggression and recognizes particular physiological substrates, it does not necessarily point to effective treatments. Eichelman and Hartwig (1990) have recognized the multiplicity of factors that can contribute to destructive behavior and have developed a coherent, standardized classification system to unite researchers and clinicians through a common nosology. With this system, a centralized database should be created whereby independent researchers can compare effective treatments in relation to very specific manifestations of destructive behavior.

Finally, these modes of behavior can be applied to forensic cases to better explicate the nature of a violent act. Forensic criteria offered by Meloy, 1988; Meloy, 1997 and Meloy, 1998 allows for better identification of particular manifestations of aggression displayed by an offender. With the support of biochemical, neuroanatomical, and pharmacological findings from the literature on animal and human aggression, forensic experts will be better able to establish the severity of pathological aggression evidenced in a crime. This level of differentiation may then offer clues as to the motivation, level of dangerousness, and risk of recidivism posed by individuals who enact aggression.

Acts of ethnic cleansing, school shootings, bombings, hostage takings, incidents of terrorism—these and other violent acts appear with regularity in both print and visual media. Indeed, worldwide communication can now broadcast scenes of violence from every corner of the world to anyone with a television, radio, or Internet connection. Moreover, advancing technology has increased the chance that at any given incident, someone with a video camera will capture the scene live, leaving little to the imagination. At least in part because of these developments, greater attention is being paid to those who inflict injury on others and to how such acts are perpetrated.

The victims of such events and the public at large can find redress from the courts. However, many questions about the nature of the person who committed the act are often left unanswered. There appears to be a subjective awareness by many that certain acts of violence are qualitatively different from others, and considerable objective data support the veracity of this observation. The legal system has recognized a distinction for years. For example, murder is prosecuted at different levels, depending on the degree to which the perpetrator planned the crime and on the level of cruelty. Legislative and judicial bodies have also attempted to address this distinction by passing hate-crime legislation and by redefining old behaviors as new crimes (e.g., stalking). Clinicians and researchers alike have been studying these behaviors since the beginning of the 20th century. Even early observers noted distinct forms and etiologies of aggression. After nearly eight decades of study, numerous experts have produced a voluminous literature revealing the complexity of aggression, which will contribute to its detection, control, and alleviation.