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- Aggression (5) (entfernen)
Aggression is one of the most researched topics in psychology. This is understandable, since aggression behavior does a lot of harm to individuals and groups. A lot is known already about the biology of aggression, but one system that seems to be of vital importance in animals has largely been overlooked: the hypothalamic-pituitary-adrenal (HPA) axis. Menno Kruk and Jószef Haller and their research teams developed rodent models of adaptive, normal, and abnormal aggressive behavior. They found the acute HPA axis (re)activity, but also chronic basal levels to be causally relevant in the elicitation and escalation of aggressive behavior. As a mediating variable, changes in the processing of relevant social information is proposed, although this could not be tested in animals. In humans, not a lot of research has been done, but there is evidence for both the association between acute and basal cortisol levels in (abnormal) aggression. However, not many of these studies have been experimental of nature. rnrnOur aim was to add to the understanding of both basal chronic levels of HPA axis activity, as well as acute levels in the formation of aggressive behavior. Therefore, we did two experiments, both with healthy student samples. In both studies we induced aggression with a well validated paradigm from social psychology: the Taylor Aggression Paradigm. Half of the subjects, however, only went through a non-provoking control condition. We measured trait basal levels of HPA axis activity on three days prior. We took several cortisol samples before, during, and after the task. After the induction of aggression, we measured the behavioral and electrophysiological brain response to relevant social stimuli, i.e., emotional facial expressions embedded in an emotional Stroop task. In the second study, we pharmacologically manipulated cortisol levels 60min before the beginning of the experiment. To do that, half of the subjects were administered 20mg of hydrocortisone, which elevates circulating cortisol levels (cortisol group), the other half was administered a placebo (placebo group). Results showed that acute HPA axis activity is indeed relevant for aggressive behavior. We found in Study 1 a difference in cortisol levels after the aggression induction in the provoked group compared to the non-provoked group (i.e., a heightened reactivity of the HPA axis). However, this could not be replicated in Study 2. Furthermore, the pharmacological elevation of cortisol levels led to an increase in aggressive behavior in women compared to the placebo group. There were no effects in men, so that while men were significantly more aggressive than women in the placebo group, they were equally aggressive in the cortisol group. Furthermore, there was an interaction of cortisol treatment with block of the Taylor Aggression Paradigm, in that the cortisol group was significantly more aggressive in the third block of the task. Concerning basal HPA axis activity, we found an effect on aggressive behavior in both studies, albeit more consistently in women and in the provoked and non-provoked groups. However, the effect was not apparent in the cortisol group. After the aggressive encounter, information processing patterns were changed in the provoked compared to the non-provoked group for all facial expressions, especially anger. These results indicate that the HPA axis plays an important role in the formation of aggressive behavior in humans, as well. Importantly, different changes within the system, be it basal or acute, are associated with the same outcome in this task. More studies are needed, however, to better understand the role that each plays in different kinds of aggressive behavior, and the role information processing plays as a possible mediating variable. This extensive knowledge is necessary for better behavioral interventions.
Stress has been considered one of the most relevant factors promoting aggressive behavior. Animal and human pharmacological studies revealed the stress hormones corticosterone in rodents and cortisol in humans to constitute a particularly important neuroendocrine determinate in facilitating aggression and beyond that, assumedly in its continuation and escalation. Moreover, cortisol-induced alterations of social information processing, as well as of cognitive control processes, have been hypothesized as possible influencing factors in the stress-aggression link. So far, the immediate impact of a preceding stressor and thereby stress-induced rise of cortisol on aggressive behavior as well as higher-order cognitive control processes and social information processing in this context have gone mostly unheeded. The present thesis aimed to extend the hitherto findings of stress and aggression in this regard. For this purpose two psychophysiological studies with healthy adults were carried out, both using the socially evaluated-cold pressor test as an acute stress induction. Additionally to behavioral data and subjective reports, event related potentials were measured and acute levels of salivary cortisol were collected on the basis of which stressed participants were divided into cortisol-responders and "nonresponders. Study 1 examined the impact of acute stress-induced cortisol increase on inhibitory control and its neural correlates. 41 male participants were randomly assigned to the stress procedure or to a non-stressful control condition. Beforehand and afterwards, participants performed a Go Nogo task with visual letters to measure response inhibition. The effect of acute stress-induced cortisol increase on covert and overt aggressive behavior and on the processing of provoking stimuli within the aggressive encounter was investigated in study 2. Moreover, this experiment examined the combined impact of stress and aggression on ensuing affective information processing. 71 male and female participants were either exposed to the stress or to the control condition. Following this, half of each group received high or low levels of provocation during the Taylor Aggression Paradigm. At the end of the experiment, a passive viewing paradigm with affective pictures depicting positive, negative, or aggressive scenes with either humans or objects was realized. The results revealed that men were not affected by a stress-induced rise in cortisol on a behavioral level, showing neither impaired response inhibition nor enhanced aggressive behavior. In contrast, women showed enhanced overt and covert aggressive behavior under a surge of endogenous cortisol, confirming previous results, albeit only in case of high provocation and only up to the level of the control group. Unlike this rather moderate impact on behavior, cortisol showed a distinct impact on neural correlates of information processing throughout inhibitory control, aggression-eliciting stimuli, and emotional pictures for both men and women. At this, stress-induced increase of cortisol resulted in enhanced N2 amplitudes to Go stimuli, whereas P2 amplitudes to both and N2 to Nogo amplitudes retained unchanged, indicating an overcorrection and caution of the response activation in favor of successful inhibitory control. The processing of aggression-eliciting stimuli during the aggressive encounter was complexly altered by stress differently for women and men. Under increased cortisol levels, the frontal or parietal P3 amplitude patterns were either diminished or reversed in the case of high provocation compared to the control group and to cortisol-nonresponders, indicating a desensitization towards aggression-eliciting stimuli in males, but a more elaborate processing of those in women. Moreover, stress-induced cortisol and provocation jointly altered subsequent affective information processing at early as well as later stages of the information processing stream. Again, increased levels of cortisol led opposite directed amplitudes in the case of high provocation relative to the control group and cortisol-nonresponders, with enhanced N2 amplitudes in men and reduced P3 and LPP amplitudes in men and women for all affective pictures, suggesting initially enhanced emotional reactivity in men, but ensuing reduced motivational attention and enhanced emotion regulation in both, men and women. As a result, these present findings confirm the relevance of HPA activity in the elicitation and persistence of human aggressive behavior. Moreover, they reveal the significance of compensatory and emotion regulatory strategies and mechanisms in response to stress and provocation, indorsing the relevance of social information and cognitive control processes. Still, more research is needed to clarify the conditions which lead to the facilitation of aggression and by which compensatory mechanisms this is prevented.
The stress hormone cortisol as the end-product of the hypothalamic-pituitary-adrenal (HPA) axis has been found to play a crucial role in the release of aggressive behavior (Kruk et al., 2004; Böhnke et al., 2010). In order to further explore potential mechanisms underlying the relationship between stress and aggression, such as changes in (social) information processing, we conducted two experimental studies that are presented in this thesis. In both studies, acute stress was induced by means of the Socially Evaluated Cold Pressor Test (SECP) designed by Schwabe et al. (2008). Stressed participants were classified as either cortisol responders or nonresponders depending on their rise in cortisol following the stressor. Moreover, basal HPA axis activity was measured prior to the experimental sessions and EEG was recorded throughout the experiments. The first study dealt with the influence of acute stress on cognitive control processes. 41 healthy male participants were assigned to either the stress condition or the non-stressful control procedure of the SECP. Before as well as after the stress induction, all participants performed a cued task-switching paradigm in order to measure cognitive control processes. Results revealed a significant influence of acute and basal cortisol levels, respectively, on the motor preparation of the upcoming behavioral response, that was reflected in changes in the magnitude of the terminal Contingent Negative Variation (CNV). In the second study, the effect of acute stress and subsequent social provocation on approach-avoidance motivation was examined. 72 healthy students (36 males, 36 females) took part in the study. They performed an approach-avoidance task, using emotional facial expressions as stimuli, before as well as after the experimental manipulation of acute stress (again via the SECP) and social provocation realized by means of the Taylor Aggression Paradigm (Taylor, 1967). Additionally to salivary cortisol, testosterone samples were collected at several points in time during the experimental session. Results indicated a positive relationship between acute testosterone levels and the motivation to approach social threat stimuli in highly provoked cortisol responders. Similar results were found when the testosterone-to-cortisol ratio at baseline was taken into account instead of acute testosterone levels. Moreover, brain activity during the approach-avoidance task was significantly influenced by acute stress and social provocation, as reflected in reductions of early (P2) as well as of later (P3) ERP components in highly provoked cortisol responders. This may indicate a less accurate, rapid processing of socially relevant stimuli due to an acute increase in cortisol and subsequent social provocation. In conclusion, the two studies presented in this thesis provide evidence for significant changes in information processing due to acute stress, basal cortisol levels and social provocation, suggesting an enhanced preparation for a rapid behavioral response in the sense of a fight-or-flight reaction. These results confirm the model of Kruk et al. (2004) proposing a mediating role of changed information processes in the stress-aggression-link.
Thema der vorliegenden Arbeit ist eine Analyse alltäglicher Rachereaktionen und rachebezogener Reaktionen unter gerechtigkeitspsychologischen Aspekten. Rache wird als eine Bewältigungsreaktion verstanden, welche mit Hilfe eines handlungstheoretischen Rahmenmodells beschrieben werden kann. Diese Konzeption will sich bewusst von jenen (vor allem in der Rechtsphilosophie vertretenen) Ansätzen, nach denen Rache eine destruktive, affektgesteuerte, irrationale Form der Vergeltung sei, abgrenzen. Besonderes Augenmerk wird auf die Frage gelegt, wo und wie sich der Einfluss gerechtigkeitsbezogener Persönlichkeitseigenschaften (Glaube an eine gerechte Welt, Sensibilität für widerfahrene Ungerechtigkeit, Soziale Verantwortung) sowie gerechtigkeitsbezogener Kognitionen und Emotionen im Prozessmodell einer Rachehandlung verorten lässt. Es wird erstens argumentiert, dass gerechtigkeitsbezogene Persönlichkeitseigenschaften (a) auf die subjektive Bedeutsamkeit gerechtigkeitsbezogener Ziele, (b) auf die Wahrscheinlichkeit, mit der von einer verfügbaren Racheaktion Gebrauch gemacht wird, (c) auf den Einsatz sekundärer Bewältigungsstrategien sowie (d) auf die Bewertung rachebezogener Ereignisse Einfluss nehmen. Zweitens wird argumentiert, dass Racheaktionen zumindest begrenzt rational in dem Sinne sind, als ihnen (im Sinne von "Erwartung-´Wert-Theorien") spezifische Kosten-Nutzen-Überlegungen zugrunde liegen. Drittens wird untersucht, inwiefern die Beobachtung eines Schicksalsschlages zu Lasten des "Täters" aus der Perspektive des "Opfers" ebenso funktional sein (d.h. aversive Emotionen reduzieren und zum Erleben von Genugtuung, Zufriedenheit und wiederhergestellter Gerechtigkeit beitragen) kann wie eine erfolgreich ausgeführte Racheaktion. Es werden vier Studien beschrieben, die die im theoretischen Teil der Arbeit entwickelten Hypothesen konsekutiv prüfen. Bei zwei Studien wird mit Vignetten gearbeitet, bei den beiden anderen handelt es sich um laborexperimentelle Untersuchungen. Die Ergebnisse dieser vier Studien zeigen, dass Rachereaktionen zumindest zu einem gewissen Anteil durch antizipatorische Kognitionen sowie durch gerechtigkeitsbezogene Persönlichkeitseigenschaften vorhergesagt werden können. Ebenso kann der Einfluss gerechtigkeitsbezogener Persönlichkeitseigenschaften auf die subjektive Bedeutsamkeit gerechtigkeitsbezogener Ziele sowie auf sekundäre Bewältigungsstrategien nachgewiesen werden. Ein beobachteter Schicksalsschlag zu Lasten des "Täters" kann zwar Ärger und Frustration auf Seiten des "Opfers" dämpfen, nicht aber Zufriedenheit, Genugtuung und die Wahrnehmung wiederhergestellter Gerechtigkeit signifikant erhöhen. Die Befunde werden vor dem Hintergrund aggressions-, gerechtigkeits- und bewältigungspsychologischer Konzepte diskutiert. Aus einer vertieften methodischen Diskussion der verwendeten Untersuchungsansätze ergeben sich darüber hinaus konkrete Vorschläge dahingehend, wie Racheaktionen und rachebezogene Reaktionen in zukünftigen Studien untersucht werden sollten.
Die vorliegende Dissertation beschäftigt sich mit der Konzeption, der Implementation und der Evaluation eines Kindertrainings für sechs- bis achtjährige Grundschüler, welches pro-soziale Verhaltensweisen, sozial-emotionale Kompetenzen und konstruktive Konfliktlösestrategien vermitteln und damit aggressivem Verhalten vorbeugen soll. Das verhaltens- und personenzentrierte Kindertraining wurde mit 92 Kindern an fünf Grundschulen der Stadt Trier von September 2003 bis Juli 2004 durchgeführt. Die Wirksamkeit des Trainings wurde im Vergleich zu einer unbehandelten Kontrollgruppe von 51 Kindern mittels Prä-, Post- und 4-Monats-Follow-up-Messungen überprüft, wobei kindliche Kompetenzen und Problemverhalten aus der Sicht der Eltern, der Klassenlehrerinnen und der Kinder mit Fragebögen bzw. Kinderinterviews erfasst wurden. Der erste Teil der Dissertation widmet sich dem theoretischen Hintergrund des IBC-Kindertrainings und beschäftigt sich mit den Phänomenen Konflikt, Aggression und prosoziales Verhalten sowie mit der Verflechtung dieser Phänomene untereinander. An eine Über-sicht zu den bestehenden Präventionsprogrammen zur Förderung von prosozialem Verhalten und zur Prophylaxe von aggressiven Verhaltensweisen bei Kindern im Grundschulalter schließt sich die detaillierte Darstellung des IBC-Trainingskonzeptes an. Vorzüge dieses Trainingsprogramms gegenüber anderen Kindertrainings werden aufgezeigt und begründet. Die methodische Vorgehensweise und die Ergebnisse der durchgeführten Trainingsevaluation werden im zweiten Teil der Arbeit vorgestellt. Es konnten positive Einflüsse des Trainings auf das Sozialverhalten der Erstklässler nachgewiesen werden. Die erzielten Trainingseffekte liegen im mittleren Bereich (.23 ≤ d ≤ .94). Insbesondere ließ sich eine signifikante Reduktion des oppositionell-aggressiven Verhaltens und der emotionalen Auffälligkeiten aufzeigen. Die wesentlichen Evaluationsbefunde zur Wirksamkeit des IBC-Kindertrainings werden im dritten Teil der Arbeit methodenkritisch diskutiert. Vor dem Hintergrund aktueller gesellschaftlicher Entwicklungen wird dabei aufgezeigt, dass das niederschwellige Angebot des evaluierten Kindertraining insbesondere in Zeiten knapper öffentlicher Mittel als eine wertvolle Chance zur Förderung kindlicher Kompetenzen und zur Vorbeugung negativer Entwicklungen genutzt werden sollte.