Premeditated aggression: clinical assessment and cognitive psychophysiology

Personality and Individual Differences 34 (2003) 773–781 www.elsevier.com/locate/paid

Premeditated aggression: clinical assessment and cognitive psychophysiology Matthew S. Stanford*, Rebecca J. Houston, Nicole R. Villemarette-Pittman, Kevin W. Greve Department of Psychology, University of New Orleans, New Orleans, LA 70148, USA Received 14 September 2001; received in revised form 17 January 2002; accepted 7 March 2002

Abstract Aggressive behavior has traditionally been classified into two distinct subtypes: an affective, impulsive aggressive display or a planned, predatory aggressive act. While a number of investigations have examined the clinical and physiological correlates in impulsive aggressive individuals, very little research has been conducted on those individuals engaging in predominantly premeditated aggressive acts. The present study compared a group of premeditated aggressive psychiatric outpatients with a group of normal, nonaggressive control subjects on personality, neuropsychological and cognitive psychophysiological measures. Consistent with previous work, premeditated aggressors did not differ significantly from controls on most measures of neuropsychological and psychophysiological function. Premeditated aggressors did show significant personality pathology scoring higher on measures of impulsivity, verbal and physical aggression, anger, hostility, psychoticism and neuroticism. Overall, these results suggest a distinctive personality style that is associated with aggressive behavior. With respect to this and previous work, it is suggested that the physiological aspects of behavioral control play a key role in the type of aggressive behavior displayed. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Event-related potentials; Neuropsychology; Personality; Aggression

Traditionally, the study of violence and aggression has recognized the importance of distinguishing between different types of destructive behavior. While a number of various physiological and behavioral categories have been described, two distinct subtypes of aggressive behavior consistently emerge: an affective or impulsive type of aggressive behavior and a predatory or premeditated type. Impulsive aggression is typically described as a reactive or emotionally charged * Corresponding author. Tel.: +1-504-280-5525; fax: +1-504-280-6049. E-mail address: [email protected] (M.S. Stanford). 0191-8869/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0191-8869(02)00070-3

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aggressive response characterized by a loss of behavioral control (Barratt, 1991; Raine, Meloy, Bihrle, Stoddard, LaCasse, & Buchsbaum, 1998). Premeditated aggression, however, is considered a purposeful, controlled aggressive display that is usually instrumental in nature. A number of studies have attempted to delineate the abnormal clinical and neurological features that characterize individuals engaging in impulsive violence (Coccaro, 1989; Houston & Stanford, 2001; Stanford, Houston, Mathias, Greve, Villemarette-Pittmann, & Adams, 2001). In addition, previous work has indicated different treatment success depending upon the type of aggressive behavior displayed (Barratt, Stanford, Felthous, & Kent, 1997). Few investigations, however, have attempted to document or describe those features that might be clinically relevant in individuals that engage in premeditated violent acts. According to Linnoila and Charney (1999), ‘‘the perpetrators [of premeditated physical aggression] are not thought to be different from nonviolent healthy volunteers on psychobiological variables.’’ Despite the recency of this statement, it appears only three studies have actually examined underlying biological substrates in premeditated violent offenders compared to impulsive violent offenders and/or normal non-violent controls (Barratt, Stanford, Kent, & Felthous, 1997; Linnoila, Virkkunen, Scheinin, Nuutila, Rimon, & Goodwin, 1983; Raine et al., 1998). In general, impulsive aggressive subjects, as compared with premeditated aggressive subjects, demonstrate lower levels of CSF 5HIAA (Linnoila et al., 1983), impaired prefrontal function (Raine et al., 1998), poorer verbal skills and lower P3 amplitude (Barratt, Stanford, Kent et al., 1997). In contrast, premeditated aggressive subjects exhibit relatively normal prefrontal function (Raine et al., 1998) and P3 amplitude (Barratt, Stanford, Kent et al., 1997b) when compared with non-violent controls. It is important, however, to note two methodological caveats in previous work related to premeditated aggression. First, all three of the investigations mentioned here utilized offender samples. This population is associated with a multitude of potential confounding variables (e.g. low IQ) that make generalization of any findings to a psychiatric setting uncertain. Secondly, the literature is replete with investigations that imply some link between psychopathy and aggression, particularly premeditated aggression (Hare, 1993). While individuals that meet criteria for psychopathy may indeed engage in overt aggressive behavior (premeditated or impulsive), it is not required or necessarily even a common characteristic of the classification. Therefore, accurate study requires explicit identification of the type and degree of aggressive behavior exhibited. With respect to these issues, the present study compared a group of premeditated aggressive psychiatric outpatients with a group of non-aggressive control subjects on measures of personality, neuropsychological performance and cognitive psychophysiology.

1. Methods 1.1. Subjects Over a 4-year period, 80 patients were referred from local outpatient psychiatric clinics for assessment due to problems with aggressive behavior. Using a semi-structured aggression interview (Barratt & Stanford, 2001), 15 patients (19%) were identified as exhibiting predominately premeditated aggressive behaviors. This interview has been used in previous studies which have shown

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significant personality, neuropsychological and psychophysiological differences between impulsive and premeditated aggressive individuals (Baratt, Stanford, Felthous et al., 1997; Baratt, Stanford, Kent et al., 1997). Interrater reliability for the interview has been shown to be high (kappa=0.79). One of the 15 premeditated individuals received an Axis II diagnosis of mental retardation and was therefore excluded from further analysis. This premeditated aggressor group (n=14, 12M/ 2F, M age=35.50, SD=13.45) was compared with a non-aggressive normal control group (n=14, 12M/2F, M age=30.50, SD=7.89). Non-aggressive controls were primarily recruited via newspaper advertisement and excluded for any of the following: aggression problems, head injury, psychoactive medications or psychiatric illness. Primary psychiatric diagnoses for the premeditated subjects were as follows: Axis I: Depression n=3; Dysthymia n=2; Axis II: Antisocial Personality Disorder n=9; Borderline Personality Disorder n=2; Narcissistic Personality Disorder n=1; Axis I & II comorbidity n=4. Five of the premeditated subjects were presently taking psychoactive medications: Wellbutrin n=2; Serax n=1; Tranxene n=1; Sinequan n=1; Risperdal n=1; Desyrel n=1; Trazadone n=1. 1.2. Personality and neuropsychological measures All subjects completed the following battery of personality and neuropsychological tests: Barratt Impulsiveness Scale (BIS-11; Patton, Stanford, & Barratt, 1995), Eysenck Personality Questionnaire (Eysenck & Eysenck, 1975), Buss–Perry Aggression Questionnaire (Buss & Perry, 1992), Brown–Goodwin Lifetime History of Aggression Questionnaire (Brown, Goodwin, Ballenger, Goyer, & Major, 1979), Peabody Picture Vocabulary Test-Revised (Dunn & Dunn, 1981), Trail Making Test (Reitan & Wolfson, 1985), Benton Facial Recognition (Benton, Sivan, Hamsher, Varney, & Spreen, 1994), Ruff Figural Fluency (Ruff, 1988), Controlled Oral Word Association Test (Lezak, 1995), and the Wisconsin Card Sorting Test (WCST; Heaton, Chelune, Talley, Kay, & Curtiss, 1993). The WCST was administered and scored in accordance with Heaton et al. (1993) except that all 128 cards were sorted rather than discontinuing administration after the completion of six categories. 1.3. Psychophysiological measures Psychophysiological recordings were taken in the afternoon (13:00–16:00 h) to control for hourly variations in scalp patterns. Subjects were seated in a comfortable chair in a sound and light attenuated room. The scalp was prepared by application of rubbing alcohol and a mildly abrasive gel (OmniPrep). An electrocap (International 10–20 system) was fitted onto each subject’s head and midline scalp electrodes (Fz, Cz, Pz) were examined. Electrodes were referenced to linked ears, and an EOG electrode was affixed below the left eye to facilitate differentiation of artifact and allow for removal of data contaminated by eye movements. Trial rejection due to artifact contamination was determined by a bin selection technique. Trials were placed into one of five bins according to the level of artifact present in the trial. Bin five contained all trials and thus the highest level of artifact. Bins four to one contained decreasing levels of artifact in conjunction with decreasing number of trials. Bin five was utilized for peak identification in 42.9% of stimuli. Bin four was utilized in 14.3%, bin 3 in 3.6%, bin two in 21.4% and bin one in 17.9%.

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Impedance for each electrode was less than 5 Kohms. EEGs and EOGs were digitized every 4 ms for a 1000 ms interval beginning 100 ms prior to stimulus onset. Physiological data were recorded using QND 3.1 (Neurodata, Inc., 1997) running on a Power Macintosh 8600/300. Signal amplification was conducted using the NE-3 amplifier. The filter bandpass was set at 0.5 to 35 Hz. 1.4. Auditory oddball task The auditory oddball task consisted of one block of 200 trials. The stimuli were two randomly sequenced tones, a frequent 1000 Hz tone and a rare 2000 Hz tone. Tones were presented in a ratio of 80/20 and were presented at a comfortable level of 70 dB through stereo headphones at a rate of one tone every 2 s, with a 5 ms rise/fall and a 50 ms sustain. Subjects were asked to sit with their eyes closed and silently count the rare 2000 Hz tones. If subjects did not report the correct count ( 5 tones), they were asked to repeat the task. In the present sample, one subject in the premeditated aggressor group was asked to repeat the task due to an incorrect count. 1.5. Statistical analyses Univariate ANOVAs were conducted to examine group differences on personality and neuropsychological measures. Age and education corrected scores were utilized on neuropsychological measures where available. Event-related potential amplitude and latency were examined using repeated measures ANOVAs with group serving as the between subjects variable and electrode site serving as the within subjects variable. P3 was defined as the most positive deflection 250+ ms after stimulus presentation. P3 peak amplitude and latency were determined from baseline (defined as the 100 ms prior to stimulus onset) using a graphical user interface program. For analysis of amplitude, the mV deflection from the baseline to the peak served as the dependent variable. In latency analysis, the dependent variable was the average milliseconds from stimulus presentation to the peak.

2. Results 2.1. Personality measures Analyses of age indicated no significant group difference [F(1, 26)=1.44, P=0.24]. In terms of personality measures, univariate ANOVAs revealed a significant group difference on the BIS-11 [F(1, 26)=5.63, P=0.025] indicating higher impulsiveness scores in the premeditated aggressor group (Table 1). Analyses of the EPQ indicated significant group differences on both the Psychoticism [F(1, 26)=10.34, P=0.003] and Neuroticism [F(1, 26)=17.69, P<0.001] Scales with the premeditated aggressor group scoring higher than non-aggressive controls (Table 1). Analysis of the BPAQ also indicated significantly higher scores on the Physical Aggression [F(1, 26) =32.33, P<0.001], Verbal Aggression [F(1, 26)=8.84, P=0.006], Anger [F(1, 26)=30.60, P<0.001] and Hostility [F(1, 26)=13.51, P=0.001] subscales as well as the Total Aggression Score [F(1,26)=29.06, P<0.001] in the premeditated aggressor group (Table 1). Finally, analysis of the

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M.S. Stanford et al. / Personality and Individual Differences 34 (2003) 773–781 Table 1 Personality measures Measure

Premeditated aggressors n=14 M

Non-aggressive controls n=14

S.D.

M

S.D.

Barratt Impulsiveness Scale

74.50*

17.69

61.21

11.21

Eysenck Personality Questionnaire Psychoticism Extraversion Neuroticism

6.64* 11.79 17.21*

4.36 4.49 5.85

2.43 14.50 9.43

2.24 5.37 3.72

35.07* 19.36* 26.00* 26.50* 106.93*

9.66 5.51 7.98 9.51 29.00

17.07 13.86 12.36 15.21 58.50

6.86 4.19 4.63 6.45 17.00

17.57*

7.45

4.21

3.51

Buss–Perry Aggression Questionnaire Physical Verbal Anger Hostility Total Brown–Goodwin Lifetime History of Aggression

*Denotes significant group difference at the < 0.05 level.

Brown–Goodwin Lifetime History of Aggression scores indicated a significantly greater history of aggressive behavior in the premeditated aggressor group [F(1, 26)=36.82, P< 0.001; Table 1]. No other significant differences were found on personality measures. 2.2. Neuropsychological measures On neuropsychological measures, no significant group differences were detected with the exception of WCST failure to maintain set [F(1, 26)=5.98, P=0.022]. Premeditated subjects exhibited more failures to maintain set. A comprehensive list of neuropsychological performance in these two groups is provided in Table 2. 2.3. Psychophysiological measures Repeated measures analysis of P3 amplitude indicated a significant main effect for site [F(2, 50) =53.07, P<0.001]. Main comparisons indicated normal P3 topography (Ant
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Table 2 Neuropsychological measures Measure

Premeditated aggressors n=14

Non-aggressive controls n=14

M

S.D.

M

S.D.

100.14

14.91

108.07

13.04

Trail Making Testb Trails A Trails B

42.43 49.71

8.86 6.89

47.07 49.21

10.19 12.85

Benton Facial Recognition

46.21

4.49

45.00

7.25

Ruff Figural Fluency Testb Number of Designs Number of Perseverations

34.60 47.71

12.92 5.61

41.93 47.65

13.54 13.44

Controlled Oral Word Association Testb FAS Animals

42.16 48.02

8.87 18.55

46.66 41.96

9.86 8.46

Wisconsin Card Sorting Testc Total Correct Total Errors Perseverative Responses Peseverative Errors Nonperseverative Errors Conceptual Level of Response (%) Number of Categories Trials to First Category Failure to Maintain Set

92.50 35.50 21.14 19.00 16.29 64.79 6.07 11.50 1.57*

15.40 15.40 11.59 10.40 7.43 18.90 3.12 1.95 1.40

96.00 33.71 21.07 18.79 14.64 60.77 7.29 17.79 0.50

20.45 18.47 13.09 10.71 8.56 25.88 3.20 14.92 0.85

Peabody Picture Vocabulary Testa

* Denotes significant group difference at < 0.05 level. a Scores reported are standard scores. b Scores reported are t scores. c Scores reported are raw scores from 128 card version.

3. Discussion Consistent with previous work, premeditated aggressors did not differ significantly from normal controls on most measures of neuropsychological and psychophysiological function (Barratt, Stanford, Kent et al., 1997). In contrast, there were pronounced differences on several measures of personality. The premeditated group scored higher on measures of impulsivity, verbal and physical aggression, anger, hostility, psychoticism and neuroticism. It is not surprising that individuals displaying premeditated aggressive behavior would show significant personality pathology. Individuals displaying chronic aggression problems, regardless of the type of aggressive

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Fig. 1. Comparison of grand average waveforms across groups.

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behavior, tend to score higher on these personality constructs (Stanford, Greve, Mathias, & Houston, 1998). High impulsivity and psychoticism scores are related to antisocial traits and behaviors (American Psychiatric Association, 1994; Eysenck & Eysenck, 1975), which would be expected in an aggressive sample, particularly those whose aggressive displays are typically premeditated in nature. Additionally, the high neuroticism scores suggest greater emotional lability and responsiveness in the premeditated aggressors. Again, this finding can easily be interpreted within the context of aggressive behavior, greater emotional lability may lead to more extreme behavioral expressions as a method of coping (e.g. physical harm). Thus, these results indicate that the individual who habitually engages in controlled aggressive acts can clearly be differentiated from normal, non-aggressive controls on measures of personality. Analysis of neuropsychological measures yielded only one significant result. The premeditated aggressors exhibited significantly more failures to maintain set on the WCST. The lack of other differences in neuropsychological performance of this group suggests that this difference is the result of an impulsive personality style rather than any significant cognitive deficit. Psychophysiological analyses indicated no significant P3 amplitude or latency differences between premeditated aggressors and normal controls. This is consistent with previous work (Barratt, Stanford, Kent et al., 1997) that demonstrated no significant P3 differences between incarcerated premeditated aggressors and non-aggressive controls. However, in terms of P3 latency, the present analysis did approach significance (P=0.06) suggesting a trend toward a longer P3 latency in the premeditated aggressive group. As with the neuropsychological finding, this result might best be interpreted with regard to the personality style of these premeditated aggressors. Prolonged P3 latency has been linked to increased attitudinal hostility (Bond & Surguy, 2000). Thus, the high levels of anger/hostility evidenced in the premeditated aggressive group may have played a role in the latency trend observed in this sample. The present results indicate a clear pattern of personality differences between premeditated aggressors and non-aggressive controls with few differences on neuropsychological and psychophysiological variables. These results in conjunction with previous work (Barratt, Stanford, Kent et al., 1997; Stanford et al., 1998), suggest a distinctive personality style that may be associated with chronic aggressive behavior, regardless of the type of aggression displayed (premeditated or impulsive). Considering these findings, it is hypothesized that the individual’s capacity to control his behavior plays a key role in the manifestation of aggressive behavior. Those who display predominately impulsive aggressive behavior are characterized by a host of cognitive and psychophysiological deficits that seem to contribute to their loss of behavioral control. Conversely, the individual engaging in predominately premeditated aggressive acts appears to have an intact behavioral control system. Thus these results provide some insight as to the underlying mechanisms of different aggressive subtypes, and allow for more accurate evaluation and treatment of such problem behavior.

Acknowledgements This research was supported by the Dreyfus Health Foundation, The Rogosin Institute, New York Hospital—Cornell Medical Center.

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