all of the psychopaths had committed a primarily instrumental murder.5 Our data suggested that nonpsychopathic offenders were certainly capable of committing instrumental offenses, but they did not show the same clear preference for or tendency toward instru- mental violence witnessed in the psychopathic offenders. There are a number of possible reasons for this finding. First, psychopathic offenders characteristically show a marked lack of empathy toward others (e.g., Levenston, Patrick, Bradley, & Lang, 2000), and this appears to extend to their crime victims. Recent research by Herpertz et al. (2001) indicated that psychopaths display a pro- found level of hypoemotionality that could effectively disallow an inhibition against acting in a violent manner if it served a selfish function. Here, psychopaths appeared to be capable of premedi- tating and carrying out ruthless, cold-blooded homicides that many nonpsychopathic (although potentially violent) individuals would be considerably less likely to consider perpetrating (also see Ab- bott, 2001). For example, one psychopathic offender (scoring at the 87th percentile on the PCL–R relative to other inmates) ad- mitted to police that he had decided to murder an ex-girlfriend because he felt that she was interfering with his new relationship, and he simply decided that murdering her would help resolve this issue. Another inmate carefully planned and murdered his wife because he stood to gain financially from her insurance policy. It is likely that few people without the affective deficit associated with psychopathy would seriously consider such acts, and even fewer would actually plan and carry them out. It is of note that previous studies have found that an inability to experience or anticipate the remorse (characteristic of psychopathy) that is often a consequence of aggressive behavior may lead to an increase in instrumental aggression (e.g., Guerra, Nucci, & Huesmann, 1994; Kingsbury et al., 1997).
It was interesting that the overall level of instrumental violence characterizing these homicides was substantially higher than ex- pected on the basis of previous contentions. However, although there seems to have been a long-standing and widely held belief that most homicides are reactive, emotional, or even irrational, there were actually few empirical data to speak to the issue prior to the current study. In fact, the current study was one of the first to look specifically at the offense of homicide in terms of rich, well-defined instrumental/reactive criteria. In our view, past con- ceptions of homicide greatly underestimated the relevance of fore- thought and instrumentality in understanding the phenomenon. The majority of murderers in this study did not “snap” and kill another person (although some did) as many might have expected. In our view, more research is needed (perhaps by interviewing the offenders themselves) to increase our understanding of why so many homicide offenders “chose” to engage in this type of violence.
Among the most important findings was that nearly all of the psychopaths had perpetrated primarily instrumental homicidal vi-
5 Note that the data reported here do not allow a determination of whether psychopaths are more likely than nonpsychopaths to commit an instrumental homicide (or less likely to commit a reactive homicide) because the prevalence of psychopathy in the general population is not clear (despite a published estimate of 1%; e.g., Hare, 1996). Nonetheless, among those who have committed a murder, nonpsychopaths are far more likely to have committed a reactive murder.
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olence and that so few had committed highly impulsive homicidal violence. It has been long understood that individuals with psy- chopathic qualities will sometimes engage in highly spontaneous, impulsive behavior in criminal and noncriminal contexts (e.g., Ellis, 1987; Hare, 1996). As noted by Newman and Schmitt (1998), “[P]sychopathic individuals are notorious for their failure to inhibit or modify behaviors that culminate in negative conse- quences” (p. 527). Given this connection with impulsivity and lack of behavioral controls, why were the homicide offenders in the current study unlikely to have engaged in primarily impulsive, reactive violence? We think that this pattern could possibly reflect selective impulsivity; that is, psychopaths may behave in a more instrumental manner (or, rather, may behave in a less reactive and impulsive manner) specifically for the offense of homicide. It is possible that when committing an act with such extreme negative consequences as with homicide perpetration (e.g., lifetime incar- ceration), psychopaths may plan their actions in a calculating fashion because the stakes are high. Although it may seem some- what paradoxical that psychopaths would still elect to murder someone after a more rational appraisal of the potentially serious costs of perpetrating the act, this process might be influenced by an undersensitive behavioral inhibition system (BIS). Some research- ers have suggested that the BIS is weaker in psychopaths who are seemingly unable to properly inhibit their behavior even when presented with serious punishment cues (e.g., Fowles, 1980).