This study finds that proactive and reactive aggression can be reliably and validly assessed by a brief self-report questionnaire with a reading age of 8 years. Confirmatory factor analysis supported the hypothesized two-factor proactive–reactive structure as a significantly better fit to the data than a one-factor aggression model, a finding that was replicated from one independent subsample to another. Key findings from prospective and concurrent assessments are that residuaiized proactive aggression at age 16 is uniquely characterized at age 7 by initiation of fights, strong-arm tactics, delinquency, poor school motivation, poor peer relationships, single-parent status, low social class families, poorly educated and unemployed fathers, substance-abusing parents, and hyperactivity, and at age 16 by psychopathic personality, blunted affect, and serious violent offending. Residualized reactive aggression was uniquely characterized at age 16 by impulsivity, hostility-aggression, social anxiety, lack of close friends, unusual perceptual experiences, odd speech, and ideas of reference. Both forms of aggression (raw scores) were associated with excessive fighting at age 7 and also at age 16 by paranoid ideation and stimulation seeking. Findings draw a differential picture of the proactively aggressive adolescent as being psychopathy-prone, seriously violent, and emanating from a poor social background, whereas the reactively aggressive adolescent is more impulsive, anxious, and having schizophrenia-spectrum characteristics hallmarked by reality distortion and information-processing abnormalities. Findings highlight the potential importance of differentiating these different forms of aggression in order to obtain a clearer understanding of the etiology of aggression in adolescents.
Dodge et al. 
have commented “The antecedents of chronic proactive aggressive behavior in the absence of high levels of reactive aggression remain elusive” (p 44). A key goal of the present study has been to help establish some of these elusive processes. By residualizing proactive aggression scores, their relationship to external variables could be more effectively isolated from reactive aggression, and a surprising number of differential relationships were observed for this form of aggression. As hypothesized, proactive aggression was differentially correlated with maternal ratings of psychopathic personality, as well as blunted affect. Other early differential relationships were consistent with their status as “fledgling psychopaths” [Lynam, 1996
]. Their strong-arm tactics, delinquency, and initiation of fights (all at age 7) are consistent with the early onset of antisocial behavior that characterizes adult psychopaths [Forth, 1995
], as are the other early factors of parental substance abuse, parental absence, negative socio-demographic home characteristics [Koivisto and Haapasalo 1996
; Marshall and Cooke, 1999
], and hyperactivity [Lynam, 1996
]. These findings suggest that proactive (but not reactive) aggression is an adolescent indicator of psychopathic personality, but it must be also recognized that not all proactively aggressive boys have a psychopathic personality.
One inconsistency in the literature concerns which of the two forms of aggression is most related to later problem behavior. While the social information-processing impairments and lack of inhibitory control in reactive aggressive individuals might suggest a more negative outcome in this group, two prior prospective studies have shown that proactive (but not reactive) aggression is related to later delinquency and criminality [Pulkkinen, 1996
; Vitaro et al. 1998
]. Although there were approximately the same number of items in each of the aggression subscales of the RPQ, proactive aggression items were endorsed much less frequently than reactive aggression items, with an effect size difference of d
= 1.35. Reactive aggression total scores were 2.55 times higher than proactive scores, suggesting that reactive aggression may be more adaptive and quasi-normative, and proactive more pathological. This is suggested not only by the relative infrequency of proactive aggression, but also by the fact that in the current study purely proactive (but not reactive) aggression scores were associated with serious violent offending up to age 16, and also that proactive aggression was more associated with negative early psychosocial processes. While proactive aggression may be indicative of a psychopathic personality, reactively aggressive children may consist of two subgroups: one showing a relatively adaptive reaction to current challenges to their social status but relatively normal long-term outcome, and the other a psychiatrically more disturbed (e.g. schizotypal) group who go on to develop longer-term problem behavior. Subgroups of reactive aggression with differential outcomes may partly account for any discrepant findings on outcome.
Prior social cognition research has shown that reactive aggression is characterized by social information-processing deficits [Crick and Dodge, 1996
; Dodge and Coie, 1987
], executive function deficits [Giancola et al., 1996
], and schizophrenia [Vitiello et al., 1990
]. Findings of the current study extend this perspective by demonstrating that residualized reactive aggression was related to schizotypal traits that reflect cognitive–perceptual deficits, specifically, unusual perceptual experiences, ideas of reference, paranoid ideation, and odd speech. It is likely that reality distortion, quasi-delusional belief systems, and paranoid ideation can result in misinterpretations of social intent, which in turn may predispose to reactive aggression. Prior research has suggested that there exists a subgroup of antisocial and violent individuals who are characterized by schizotypal features [e.g. Raine et al., 1999
]. In complementary fashion, recent research has identified a subgroup of schizotypal individuals characterized by impulsivity, anger/hostility, and self-damaging acts [Torgersen et al., 2002
]. The current findings give rise to the provisional hypothesis that such subgroups are particularly characterized by reactive forms of aggression and antisocial behavior, and extend the personality correlates of reactive aggression from the realms of impulsivity and social anxiety into schizotypal symptomatology. In contrast, the type of aggression and violence linked with schizophrenia-spectrum disorders is less likely to be linked to the more planned and regulated proactive form of aggression, although it should be noted that both reactive and proactive aggression were linked to paranoid ideation, while proactively aggressive children also showed the blunted affect that might be expected of psychopathic-like adolescents.
Despite several consistencies in the literature of reactive and proactive aggression, there are also inconsistencies. In addition to the issue of behavioral outcome noted above, some studies have provided mixed support for the notion of information-processing deficits in reactive aggressives [e.g. Dodge et al., 1997
]. Similarly, while some studies find reactively aggressive children to be unpopular and victimized [e.g. Schwartz et al., 1998
], some studies find proactively aggressive children to be more unpopular with peers [e.g. Dodge et al., 1997
]. Furthermore, gender differences in the correlates of proactive and reactive aggression [Connor et al., 2003
], including long-term outcome [Pulkkinen, 1996
], have been reported, and consequently the current findings from males may or may not generalize to females. Kempes et al. 
have also argued that differences in age in the populations studied could in part account for discrepancy in findings. The use of a self-report measure of reactive–proactive aggression such as the RPQ in future studies of both male and female adolescents and young adults could help extend research on these forms of aggression and help provide a resolution to broader inconsistencies in the literature.
The significant relationships emerging for residualized proactive and reactive aggression were of modest size, with effect sizes (Cohen’s d
) ranging from 0.22 to 0.74 [Cohen, 1988
]. On the one hand, this underscores the fact that distinctions between proactive and reactive aggression may exist more in degree than in absolute kind, and that these subtypes of aggression have much in common. Alternatively, residualized scores are less reliable than raw scores because they contain a higher proportion of error variance [Cronbach, 1970
]. As such, effect sizes for these residualized scores should be viewed as conservative floor estimates of the true effect, and that differences between proactive and reactive aggression may well be underestimated in this study. Nevertheless, residualization of proactive and reactive scores against each other provides a stringent test of differential effects, and can offer a valuable method in future studies for assessing the unique differences between proactive and reactive aggression. Such residualized scores also have the advantage of being free of the shared method variance confound which is a significant problem in some studies. Future studies using structural equation modeling could provide an alternative approach to dealing with error variance and potentially produce stronger effect sizes than those obtained here.
Results as a whole are generally supportive of models of proactive and reactive forms of aggression. Furthermore, findings address several gaps in the literature. To our knowledge, there has been only one prior study of proactive and reactive aggression in adolescence [Pulkkinen, 1996
], a critical time in the development of aggressive behavior. Few prior studies have demonstrated prospective relationships between early psychosocial factors in childhood and proactive–reactive aggression 9 years later in a large community sample. Importantly, there have been few demonstrations of the differential characteristics of proactive and reactive aggression controlling for each form of aggression. While studies with multiple informant sources have significant advantages, self-reports have the significant advantage that the intrinsic motivation for the aggressive act, and which forms the critical distinction between proactive and reactive aggression, is best know to the individual and may be obscure to independent observers. Future understanding of aggression must account for the heterogeneity of aggression, and the RPQ provides a brief but reliable and valid self-report instrument to help further this process.