Rebecca J. Houston

Characterizing Aggressive Behavior

In the research literature, aggressive behavior has traditionally been classified into two distinct subtypes, impulsive or premeditated. Impulsive aggression is defined as a hair-trigger aggressive response to provocation with loss of behavioral control. Premeditated aggression is defined as a planned or conscious aggressive act, not spontaneous or related to an agitated state. The present study outlines the development of a clinically useful self-report instrument, the Impulsive/Premeditated Aggression Scales (IPAS), designed to characterize aggressive behavior as predominately impulsive or predominately premeditated in nature. The IPAS showed strong reliability and validity. Analysis of the IPAS scores demonstrated the presence of two types of aggressive behavior, impulsive and premeditated, in men referred for anger problems. The aggression of most individuals in the present sample was characterized as predominately impulsive in nature (90%).

Detecting Malingered Neurocognitive Dysfunction Using the Reliable Digit Span in Traumatic Brain Injury

This study assessed the effectiveness of Greiffenstein’s Reliable Digit Span (RDS) score for the detection of malingered neurocognitive dysfunction. Participants were 54 traumatic brain injury patients referred for neuropsychological evaluation. Twenty-four met the Slick, Sherman, and Iverson criteria for at least probable malingered neurocognitive dysfunction. The control group was composed of 30 patients without external incentive and who thus did not meet the Slick criteria. All patients completed the digit span test as part of either the WAIS-R or WAIS-III. The RDS scores were calculated, and sensitivity, specificity, and predictive power were examined for several cutoffs. Classification accuracy for the RDS was excellent. Issues related to the clinical application of this technique are discussed.

Premeditated aggression: clinical assessment and cognitive psychophysiology

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, non-aggressive 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.

A comparison of anticonvulsants in the treatment of impulsive aggression.

This study compared the behavioral effects of 3 anticonvulsants in impulsive aggressive men. In a double-blind, placebo-controlled, parallel groups design, participants were randomly assigned to 1 of 4 6-week treatments: phenytoin (n = 7), carbamazepine (n = 7), valproate (n = 7), or placebo (n = 8). The efficacy measure was the average aggression score, a global severity index from the Overt Aggression Scale (J. M. Silver & S. C. Yudofsky, 1991). Analysis showed a significant reduction in impulsive aggression during all 3 anticonvulsant conditions compared with placebo. However, the treatment effect during carbamazepine administration was slightly delayed compared with phenytoin and valproate. These findings suggest that increased use of anticonvulsants could make a significant impact in the control of impulsive aggression in both mental health and criminal justice settings.

Detecting malingered performance on the Wechsler Adult Intelligence Scale: Validation of Mittenberg's approach in traumatic brain injury

This study assesses the effectiveness of the Wechsler Adult Intelligence Scale (WAIS) performance validity markers devised by Mittenberg et al. [Prof. Psychol.: Res. Pract. 26 (1995) 491] in the detection of malingered neurocognitive dysfunction (MND). Subjects were 65 traumatic brain injury (TBI) patients referred for neuropsychological evaluation. Twenty-eight met the Slick et al. [Clin. Neuropsychol. 13 (1999) 545] criteria for at least probable MND. The control group was comprised of 37 patients without external incentive and who thus did not meet the Slick et al. criteria. All subjects completed the Wechsler Adult Intelligence Scale-Revised (WAIS-R or WAIS-III). The discriminant function score (DFS) and the vocabulary-digit span (VDS) difference score were calculated and sensitivity, specificity, and predictive power were examined for several cut-offs for each marker individually and the two combined. Classification accuracy for the DFS was acceptable and better than for VDS. The use of the two markers in combination resulted in no incremental increase in classification accuracy. Issues related to the clinical application of these techniques are discussed.

Detecting Malingered Performance With the Wisconsin Card Sorting Test: A Preliminary Investigation in Traumatic Brain Injury

The present study examined the classification accuracy of four potential Wisconsin Card Sorting Test malingering indicators (Bernard and Suhr formulas and two types of Unique responses). Participants were 89 traumatic brain-injury (TBI) patients assigned to malingering and nonmalingering groups on the basis of the Slick, Sherman, and Iversion (1999) criteria. Individual Sensitivities were greater than .33 with acceptable Specificity. Combined Sensitivity for two of the indicators was greater than .60. Overall, this study demonstrated three distinct approaches to the WCST used by probable malingerers. The clinical relevance of these findings and directions for future research are discussed.

Impact of threat relevance on P3 event-related potentials in combat-related post-traumatic stress disorder.

The purpose of this study was to examine electrophysiological response to trauma-relevant stimuli in combat-related post-traumatic stress disorder (PTSD). Study design incorporated comparison of 10 Vietnam War veterans with PTSD diagnosis to 10 Vietnam War veterans with no mental disorder diagnosis on P3 components in a series of two oddball tasks (trauma-relevant threat, trauma-irrelevant threat) counterbalanced for order. Each task included high probability emotionally neutral distractor words and low probability neutral target words, but differed in the content of low probability threat words. Whereas threat words in the trauma-relevant oddball task pertained directly to combat trauma, threat words in the trauma-irrelevant oddball task were socially threatening words. Results revealed that, in comparison to healthy combat veterans, those diagnosed with PTSD demonstrated: (a) attenuated P3 response to neutral target items at selected electrode sites across both oddball tasks; and (b) increased responsivity to trauma-relevant combat stimuli but not to trauma-irrelevant social-threat stimuli at frontal electrode sites (F3, F4). Results are consistent with resource allocation models of PTSD, which suggest that PTSD is characterized by attentional bias to threat stimuli at the expense of attention to emotionally neutral information.

A double-blind placebo-controlled crossover study of phenytoin in individuals with impulsive aggression

The present study examines the behavioral and psychophysiological effects of phenytoin (PHT) in individuals who display impulsive-aggressive outbursts. In a double-blind placebo-controlled crossover design, individuals meeting previously established criteria for impulsive aggression were administered PHT and placebo during separate 6-week conditions. The efficacy measures used were the Overt Aggression Scale (OAS) and the Profile of Mood States (POMS). Psychophysiological measures (evoked potentials) were taken at baseline and at the end of each 6-week condition. Photic stimulation was used to evoke the mid-latency P1-N1-P2 waveform complex. Analysis indicated a significant decrease in the frequency of impulsive-aggressive outbursts during PHT administration compared to baseline and placebo. Analysis of the psychophysiological data showed significantly increased P1 amplitude and significantly longer N1 latency during PHT administration. In addition, a reduction in N1 amplitude during PHT administration was also suggested. These findings indicate reparation of physiological abnormalities previously observed in impulsive-aggressive individuals and imply more efficient sensory processing and effective orienting of attention. Taken together, these results provide insight as to the physiological mechanisms by which PHT serves to ameliorate impulsive-aggressive behavior.

Mid-latency evoked potentials in self-reported impulsive aggression

The present study was conducted to examine psychophysiological differences in arousability among individuals who display impulsive aggressive outbursts. Amplitude and latency for the mid-latency evoked potentials (P1, N1 and P2) were obtained at scalp electrode sites. The evoking stimuli were three intensities (low, medium, high) of photic stimulation. Compared to non-aggressive controls, impulsive aggressive subjects showed significantly reduced P1 amplitude, which is indicative of an inefficient sensory gating mechanism. In addition, these subjects exhibited significantly larger N1 amplitude implying an enhanced orienting of attention to stimuli. Impulsive aggressive subjects also exhibited shorter P1, N1 and P2 peak latency. These results suggest that impulsive aggressive individuals may display quicker orienting and processing of stimuli in an attempt to compensate for low resting arousal levels. Finally, impulsive aggressive subjects augmented the P1-N1 component more frequently than controls, which is consistent with previous studies examining impulsivity and sensation seeking. Together, these findings extend previous work concerning the underlying physiology of impulsive aggression. It has been suggested that impulsive aggressive individuals may attempt to compensate for low resting arousal levels by engaging in stimulus seeking behaviors. Accordingly, the present findings imply similar physiological compensatory responses as demonstrated by heightened orienting of attention, processing and arousability. In addition, a compromised sensory gating system in impulsive aggressors may exacerbate such circumstances, and lead to later cognitive processing deficits.

A test of the reactive aggression-suicidal behavior hypothesis: Is there a case for proactive aggression?

A large body of literature suggests that aggressive behavior can be classified into two subtypes--reactive aggression (RA) and proactive aggression (PA)--which differ on dimensions of emotional arousal, control, and impulsivity. A longstanding hypothesis posits that RA underlies the association between aggression and suicidal behavior, with the implicit assumption that PA is unrelated to suicidal behavior. However, no empirical study to date has specifically investigated this question. The authors examined associations of RA and PA with suicide attempts and suicidal ideation among 878 male and female patients in substance-dependence treatment programs. They also examined the moderating effects of sex. Contrary to hypotheses, PA was associated with both suicide attempts and suicidal ideation. RA was also associated with both outcomes in unadjusted analyses but became nonsignificant for suicide attempts in multivariate analyses. Moreover, sex served as a moderator, with PA showing an association with suicide attempt among men but not women. Results indicate the need for additional studies of PA and suicidal behavior.