Martijn van Teffelen

Chapter 8 172 lab (i.e., social exclusion and insult) and examined how they interact with psychopathic and narcissistic personality traits. We selected two procedures based on methodological similarity and expected them to have an equal impact on aggressive behavior, negative affect, and perceived threat. The results confirmed the hypothesis that social exclusion and insult had a similar impact on hostility. Findings also revealed a negative relationship between perceived threat and initial aggressive responding in people with elevated levels of narcissism after an insult. The results further showed a negative relationship between change in negative affect and aggressive behavior in people with psychopathic traits. Hopefully, identifying how hostility relates to pathological personality traits provides novel insight into what intervention works for who. An important intervention that has proven to be effective in reducing hostility is cognitive restructuring (CR). In chapters 4 and 5 , it was investigated whether enriching CR with “mental imagery” increases its efficacy. People with increased hostility levels were randomly assigned to one session of CR, imagery-enhanced CR (I-CR) or an active control intervention (AC). Changes in hostile thoughts, aggressive inclinations, state anger, and hostility traits were measured at baseline, post-intervention and one week after the intervention (follow-up). Subjects were also confronted with an emotional stressor (i.e., reimagining an autobiographical anger-evoking event) one week after the intervention. We expected I-CR to be more efficacious in reducing hostile beliefs, aggressive inclinations, state anger, and hostility traits, compared to CR and AC. Results showed that hostile thoughts, aggressive inclinations, and state anger indeed decreased more strongly after I-CR and CR compared to AC. In addition, I-CR was sustainably more efficacious in reducing hostile thoughts and aggressive inclinations compared to AC and CR. All interventions reduced hostility traits over time. Another way to advance the treatability of hostility is to develop and implement novel interventions. One intervention that could be potentially efficacious in reducing hostility is cognitive bias modification for hostile interpretation bias (CBM-I). Chapter 6 describes the development of a new CBM-I intervention and how it was tested in two experiments. The first experiment tested the feasibility of CBM-I compared to an active control (AC) condition in a small male mixed patient-community sample. The second experiment described a randomized, controlled experiment in a large group of people with clinical hostility levels. It was hypothesized that in the first experiment, CBM-I would lead to a stronger increase in benign bias and a stronger decrease in hostile bias. In the second experiment, in addition to an improvement in interpretation bias, a stronger decrease in state and trait hostility was expected compared to AC. The second experiment also explored whether CBM-I had beneficial carry-over effects on working alliance, when participants underwent psychotherapy after the experiment. Results confirmed that CBM-I increased benign bias in both experiments. In addition, the second, larger experiment showed that CBM-I led to a greater decrease in