Individual differences in the study of human aggression

Excessive concern for simplicity has often led us to underestimate the complexity of aggression. Over the years, several scales related to aggression have been identified and validated both on adults and on children. Ultimately, two main higher order dimensions, emotional responsivity and proneness to aggression, repeatedly emerged in a series of second-order factor analysis. These dimensions are rather similar to two of the big five factors of personality: neuroticism/emotinal stability and hostility/agreeableness, respectively. Several studies corroborate the plausibility of a higher level bidimensional conceptualization of aggression that, while preserving the heuristic validity of looking for more specific constructs of aggression, can link the field of aggression to the field of personality. © 1994 Wiley-Liss, Inc.     

Individual differences and measures of aggression in laboratory studies

After inducing hostility toward a confederate by threatening subjects' self-esteem, subjects were then given the opportunity either to deliver shocks (Experiment 1) or to withhold rewards (Experiment 2) from their confederate. Physiological measures were taken prior to the hostility induction, shortly after the induction and, finally, after the opportunity to aggress. Measures of individual differences relating to aggressive behavior were also considered. While the experimental manipulation was the best predictor in the ‘withholding rewards’ condition, measures of dissipation-rumination tendencies and emotional vulnerability were the best predictors in the ‘shock administration’ condition. In both conditions, systolic blood pressure seemed to reflect differences in arousal as a function of the hostility induction procedure, while subjects in the withhold rewards procedure also showed a decrease in systolic pressure after having an opportunity to aggress toward the confederate. It was concluded that not only is the withholding of rewards a more ethically acceptable procedure than shock administration, but it is also more likely to reflect experimental rather than individual difference affects.     

Individual differences in trait rumination and the neural systems supporting cognitive reappraisal

Cognitive reappraisal can alter emotional responses by changing one’s interpretation of a situation’s meaning. Functional neuroimaging has revealed that using cognitive reappraisal to increase or decrease affective responses involves left prefrontal activation and goal-appropriate increases or decreases in amygdala activation (Ochsner, Bunge, Gross, & Gabrieli, 2002; Ochsner, Ray, et al., 2004). The present study was designed to examine whether patterns of brain activation during reappraisal vary in relation to individual differences in trait rumination, which is the tendency to focus on negative aspects of one’s self or negative interpretations of one’s life. Individual differences in rumination correlated with increases in amygdala response when participants were increasing negative affect and with greater decreases in prefrontal regions implicated in self-focused thought when participants were decreasing negative affect. Thus, the propensity to ruminate may reflect altered recruitment of mechanisms that potentiate negative affect. These findings clarify relations between rumination and emotion regulation processes and may have important implications for mood and anxiety disorders.     

Individual differences at high perceptual load: the relation between trait anxiety and selective attention

Attentional control theory (Eysenck et al., 2007) posits that taxing attentional resources impairs performance efficiency in anxious individuals. This theory, however, does not explicitly address if or how the relation between anxiety and attentional control depends upon the perceptual demands of the task at hand. Consequently, the present study examined the relation between trait anxiety and task performance using a perceptual load task (Maylor & Lavie, 1998). Sixty-eight male college students completed a visual search task that indexed processing of irrelevant distractors systematically across four levels of perceptual load. Results indicated that anxiety was related to difficulty suppressing the behavioural effects of irrelevant distractors (i.e., decreased reaction time efficiency) under high, but not low, perceptual loads. In contrast, anxiety was not associated with error rates on the task. These findings are consistent with the prediction that anxiety is associated with impairments in performance efficiency under conditions that tax attentional resources.     

Individual differences in trait anxiety and goal-commitment predict updating efficiency on the reading span task

According to attentional control theory (ACT; Eysenck et al. in Emotion 7(2):336–353, 2007) anxious individuals recruit motivation on demanding tasks, which helps prevent performance shortfalls. We used a quasi-experimental design to examine the relationship between trait anxiety (operationalised using questionnaire scores), situational stress (manipulated using ego threat instructions) and motivation (indexed using a self-report goal-commitment scale) in predicting effectiveness (accuracy) and efficiency (accuracy divided by RT) on the reading span task. After controlling for depression, the variables were not related to effectiveness; however there was a significant trait anxiety × goal-commitment interaction on reading span efficiency. Higher trait anxiety predicted better efficiency at higher goal-commitment, and poorer efficiency at lower goal-commitment, and these relationships were independent of situational stress. Results are interpreted in terms of ACT.     

Individual aggression and a violent society

The first was [a woman], 32, waiting for a bus on San Francisco's Geary Boulevard at 7:57 one evening last week. A man stepped up to her, shot her twice fatally in the chest, and ran back to a waiting dark-colored Cadillac. Ten minutes later and eight blocks away ? a retired Coast Guardsman who had turned 69 that day was struck down by three bullets in the back and belly. At 9:15, near Market Street, octogenarian ? died instantly from two bullets in his back. Three miles south, at 9:50, [a woman], 45, was cut down as she stood in the doorway of a laundromat. And ten blocks away, at 10:10, [another woman], 23, the mother of a four-month-old boy, was climbing the stairs to her new house when a man walked up and said amiably, “Hi, howya doin'?” [She] turned to reply, and a bullet burrowed through her body to her spine, possibly paralyzing her for life. (“Crime: Nothing Personal,'Newsweek February 11, 1974.)     

Individual differences in trait urgency moderate the role of the affect heuristic in adolescent binge drinking

This study investigated the roles of the affect heuristic and outcome beliefs in explaining the relationship between negative urgency and adolescent binge drinking behaviour. The sample consisted of 391 Australian high school students, who were selected to be low or high on urgency. We hypothesised that highly urgent adolescents would be more likely than adolescents low in urgency to utilise the affect heuristic (i.e., to rely upon affective input) when making alcohol-related decisions. Multiple-group path analysis supported this prediction. Adolescents high in urgency exhibited greater use of the affect heuristic by displaying a direct path from affective associations to binge drinking; whereas adolescents low in urgency exhibited greater reliance upon rational processing by displaying an indirect path via outcome beliefs.     

Individual differences in autistic trait load in the general population predict visual working memory performance

Prior studies have reported instances of both intact and impaired working memory (WM) performance in people with autism spectrum disorder (ASD). In order to investigate the relation between autistic traits that extend into the normal population and WM, 104 normal college-aged students who varied in their levels of autistic traits were tested. The loading of ASD-associated traits in the normal population leads to differing predictions about WM performance. ASD traits related to a local processing style (or “attention to detail”) might enhance WM while ASD-associated traits related to difficulty switching attention and reorienting focus (or “social interaction”) might impair WM performance. To assess these predictions, participants filled out the Autism Spectrum Quotient (AQ) and performed a working memory task with both visual and verbal variants. AQ scores were then broken into “attention to detail” and “social interaction” factors, as proposed by Hoekstra and colleagues. The results showed that AQ scores did not predict verbal WM performance but they did predict visual WM performance. The social interaction and attention to detail factors of the AQ had opposing relationships with visual WM performance: A higher level of social difficulty was associated with significantly poorer visual WM performance while a higher level of attention to detail was associated with enhanced visual WM performance. Further investigation of the relation between AQ and WM using the original five-factor model proposed by Baron-Cohen and colleagues (2001) revealed an association between impoverished imagination and visual WM overall.     

Individual differences in motives for regulating affect intensity: positive trait affect and the value of trait-consistent affect

We examined individual differences in the motivation to regulate affect intensity. In three samples (total n?=?1082) we used structural equation modeling and found support for a serial mediation model in which positive trait affect predicted the motivation to increase the intensity of positive affect and decrease the intensity of negative affect, indirectly, through the commonality and value of positive affect. These findings indicate that trait affect drives regulation motives for multiple parameters of affect: people most value, and are motivated to feel, moods and emotions that match their typical experiences on intensity as well as valence.

     

Individual differences in anxiety trait are related to spatial learning abilities and hippocampal expression of mineralocorticoid receptors

Although high levels of anxiety might be expected to negatively influence learning and memory, it remains to be shown whether individual differences in anxiety may influence spatial learning and memory in outbred rat populations. We have studied this possibility in male Wistar rats whose levels of anxiety were first characterized as either high (HA) or low (LA) according to their behavior in the elevated plus maze or in the open field test. Subsequently, their performance in the Morris water maze was studied, a task dependent on hippocampal activity. Interestingly, LA rats showed a faster acquisition and better memory in the water maze when compared to HA rats. Indeed, this difference in performance could mainly be attributed to the increase in thigmotactic behavior (swimming in circles close to the maze walls) displayed by HA rats during spatial navigation. Glucocorticoids are known to affect the state of anxiety and the hippocampus is the main target of glucocorticoids in the brain. Hence, we investigated whether the hippocampal expression of the two classical corticosteroid receptors, mineralocorticoid (MR) and glucocorticoid (GR) differed in the two groups of rats. We found that LA rats displayed higher hippocampal expression of MR but not GR than HA rats. Indeed, the expression levels for these receptors were positively correlated with the amount of time spent by the animals in the open arms of the elevated plus maze. Moreover, we present evidence that the levels of anxiety quantified in the first stages of our study constitute a trait rather than a state. Taken together, this study has generated evidence of a close interaction between the anxiety trait, hippocampal MR expression and the learning abilities of individuals in stressful spatial orientation tasks.     

Altruism and aggression: the heritability of individual differences

Five questionnaires measuring altruistic and aggressive tendencies were completed by 573 adult twin pairs of both sexes from the University of London Institute of Psychiatry Volunteer Twin Register. The questionnaires measured altruism, empathy, nurturance, aggressiveness, and assertiveness. The intraclass correlations for the five scales, respectively, were .53, .54, .49, .40, and .52 for 296 monozygotic pairs, and .25, .20, .14, .04, and .20 for 179 same-sex dizygotic pairs, resulting in broad heritability estimates of 56%, 68%, 70%, 72%, and 64%. Additional analyses, using maximum-likelihood model-fitting, revealed approximately 50% of the variance on each scale to be associated with genetic effects, virtually 0% with the twins' common environment, and the remaining 50% with each twins' specific environment and/or error associated with the test. Correcting for the unreliability in the tests raised the maximum-likelihood heritabilities to approximately 60%. Age and sex differences were also found: altruism increased over the age span from 19 to 60, whereas aggressiveness decreased, and, at each age, women had higher scores than men on altruism and lower scores on aggressiveness.     

Sex differences in instigative aggression

The instigative aggression paradigm, in which male and female subjects instructed a female confederate which shock to set for an opponent in a competitive reaction time task, was employed. It was observed that males instigated more aggression than females and that both passive and assertive noncooperation effectively reduced instigative aggression, the assertive form of noncooperation being only slightly less effective. Questionnaire data suggested that females found the passive noncooperator most desirable while males found her least so. Results were discussed in terms of violation of task role and sex role expectations.     

Individual differences in cognitive-flexibility: the influence of spontaneous eyeblink rate, trait psychoticism and working memory on attentional set-shifting

Individual differences in psychophysiological function have been shown to influence the balance between flexibility and distractibility during attentional set-shifting [e.g., Dreisbach et al. (2005). Dopamine and cognitive control: The influence of spontaneous eyeblink rate and dopamine gene polymorphisms on perseveration and distractibility. Behavioral Neuroscience, 119(2), 483-490]. Here we replicate both the facilitatory and detrimental influence of spontaneous eyeblink rate upon switch costs across the two distinct conditions of a set-shifting task. We extend this by presenting additional, putatively dopamine related, individual differences that also influence attentional control. Whereas trait psychoticism showed a pattern of effects opposite to that of eyeblink rate, greater working memory served to decrease switch costs across both conditions. These results highlight the need for further exploration of the role of dopaminergic neurotransmission and component processes involved in such attentional paradigms, and illustrates the importance of considering individual differences in cognitive control.     

Relationship between team identification and trait aggression: a replication

Research yielded no significant relationship between sport fandom and trait aggression. The current study replicated previous efforts using the Buss-Perry Aggression Questionnaire, an updated version of the Buss-Durkee Hostility Inventory. In contrast to past work, the current study did yield a significant relationship between fandom and aggression for men.     

Reactive and proactive aggression: Similarities and differences

The purpose of the current study was to elaborate the nomological net surrounding the constructs of reactive (RA) and proactive aggression (PA). Typically examined in the context of children, the current study utilized a sample of 211 young adults to examine the relations between reactive and proactive aggression and measures of general personality and social information processing, as well as maladaptive behavioral correlates such as crime, substance use, and riskier sex. Both raw and residualized scores were examined. Using raw scores, the primary differences between RA and PA were related to Neuroticism (i.e., RA more strongly related) and externalizing behaviors (i.e., PA more strongly). The authors comment on the similarity of findings when using raw scores and the divergence of findings using residualized scores and argue for a cautious interpretation of differences based on residualized scores. The authors conclude that the role of Neuroticism warrants further exploration as a means for understanding the heterogeneity of aggressive behavior.     

Individual differences in Pollyannaism

The Pollyanna Principle states that people process pleasant information more accurately and efficiently than less pleasant information. This study examined whether different measures of Pollyanna tendencies are correlated with each other. Fourteen measures of Pollyannaism were derived for 133 students. The results showed that subjects who rated themselves as optimistic or happy also showed Pollyannaism on other measures of happiness, believed that the events in their lives were pleasant, gave themselves positive ratings on personality characteristics, recalled pleasant words more often than unpleasant words, supplied more free associations to pleasant stimuli than to unpleasant stimuli, listed pleasant items first, and judged that pleasant words were more frequent in the English language.     

Fantasy as a medium for the reduction of trait versus state aggression

In the first phase of an experiment reducing hostility through fantasy, 203 first and second-year high school students completed a daydreaming scale, Rotter ISB, and a sociometric scale designed to ascertain which of their peers behave aggressively. The students of the upper and lower quarters of the daydreaming scale were classified as high and low fantasy, and as aggressive or nonaggressive subjects. The second phase, two weeks later, consisted of 94 subjects forming three groups: a trait aggressive group, a nonaggressive control group, and a group of nonaggressive subjects experimentally manipulated for aggression. Half of the subjects composed stories to four high-cue aggressive TAT cards; the other half read neutral stories. All the subjects then again completed the Rotter ISB which was scored for aggression. Analysis of covariance of the scores indicated that a reduction in hostility occurred only for the group experimentally aroused to aggression in the TAT condition. The scores of the trait-aggressive subjects, tested in a before-after analysis, showed an increase in their hostility level. Fantasy capacity did not influence the scores.     

Individual and sex differences in reminiscence

Inverted alphabet printing, rotary pursuit, and mirror tracking tasks were administered to 84 subjects in order to ascertain (a) reproducibility of reminiscence scores within and between tasks and (b)sex differences in reminiscence. With prerest performance levels held constant by second-order partial correlation procedures, reproducibility of individual reminiscence differences within tasks was significant but quite low, while predictability of reminiscence from one task to another was negligible. The sexes reminisced essentially alike on inverted alphabet printing, but females reminisced more than males on the other tasks, presumably because they were relatively more depressed by massed practice on these tasks. Thus, individual and sex differences were essentially task specific. Implications of results for reminiscence theories and for the credibility of alleged relationships between reminiscence and other organismic variables were discussed.