Aggressive behaviour is a complex phenomenon, and many theories have been put forth attempting to describe its nature and explain its origins. The most common and well-established approach is to define aggressive behaviour based upon its underlying motivation, distinguishing between reactive aggression and instrumental aggression. While reactive aggression has been defined as any automatic and emotional aggressive behaviour that occurs as a response to a perceived threat or provocation [1, 2], instrumental aggression relates to aggressive behaviour with the purpose of achieving certain goals or gaining social status [3, 4]. Although this distinction has been repeatedly criticized , meta-analyses have confirmed that human aggressive behaviour has two different facets , and that a distinction must be made. Undoubtedly, there is a reactive form with the purpose of repelling a particular threat. This is associated with a high state of arousal and a negative emotional state. It is the struggle to reduce this negative arousal that motivates and drives this aggression. This form of aggression has been examined extensively in numerous laboratory and field studies. In contrast to this, another form of aggression, termed ‘appetitive aggression’, has been put forth in recent years, based on anthropological observations of cruel human behaviour [7, 8]. This is not driven by self-defence or secondary rewards, such as resources or status, but is motivated by the primary intrinsic enjoyment of the aggressive act itself. Appetitive aggression increases positive arousal and seems rewarded by the exposure to cues of violence, like the suffering of the victim or the preparation for hunting down humans . Our research group has examined appetitive aggression in many different studies from a variety of different populations, including the Democratic Republic of Congo (DRC), Rwanda, Uganda, and also with German World War II veterans, encompassing more than 2000 participants. We found that appetitive aggression, conceived as the perpetration of violence and/or the infliction of harm to a victim for the purpose of experiencing violence-related heroism and enjoyment, is indeed very common amongst former combatants. In these studies, we administered the Appetitive Aggression Scale (AAS, ), which focuses particularly upon a sense of positive arousal (e.g. ‘Is it exciting for you if you make an opponent really suffer?’, ‘Is defeating the opponent more fun for you, when you see them bleed?’, ‘Once you were used to being cruel, did you want to be crueller and crueller?’). Appetitive Aggression was so high in some of the participants that they even reported a craving to behave cruelly during their time in combat. Thus, besides the secondary rewards that can be gained as a consequence of aggressive behaviour in general, the perpetration of violence itself can be self-rewarding and facilitate the outbreak of cruelty.
Moreover, besides the aforementioned appetitive reward, the disposition to aggressive behaviour has an additional beneficial characteristic in regard to mental health and is related to the processing of cruelty: An actual or threatened death, serious injury, or threat to the physical integrity of self or others is potentially traumatic. The killing of a victim might therefore fulfil the diagnostic criteria for a traumatic event according to DSM IV. As shown by a number of studies with victims of violence, the greater the exposure to traumatic event types, the greater the risk for the development of trauma-spectrum disorders, including posttraumatic stress disorder (PTSD; ). This is not a simple dose–response effect, as the variety of traumatic stressors also counts, and thus the effect has been termed the ‘building-block-effect’. While it leads to widespread mental suffering amongst victims, this does not appear to be the case for perpetrators . Consequently, there has to be a protective mechanism that prevents the perpetrator from becoming mentally ill and dysfunctional in response to their violent behaviour. Our previous investigations suggest that it is appetitive aggression that reduces vulnerability for traumatic stress [11, 12]. Perpetrators seem to be able to tolerate a greater exposure to violence and traumatic stressors, and will only suffer from PTSD after having been exposed to an extremely high amount of trauma .
After one of the longest internal armed conflicts in the world, among guerrilla groups, paramilitary organizations and the Colombian army, Colombia is trying, through systematic demobilization of the illegal groups, to build peace. The two largest guerrilla groups in Latin-America, Fuerzas Armadas Revolucionarias de Colombia (FARC) and Ejercito de Liberacion Nacional (ELN), as well as the paramilitaries and anti-guerrilla group (AUC) have been involved in serious atrocities like killings, massacres, kidnappings or the use of landmines and booby traps. Amnesty International estimates that, in the past 20 years, more than 70,000 people have been killed, while thousands have been kidnapped, tortured or forcibly abducted to serve in one of the armed forces . In 2002, the government started negotiations with the paramilitary forces and guerilla groups, to promote the individual demobilization of combatants from all groups, and the collective demobilization for the paramilitary forces Laplante & Theidon, (2006, ) focusing on individual demobilization. One idea of these Disarmament, Demobilization and Reintegration (DDR) programmes is that the government has to create an attractive environment for former combatants, by fostering physical security and economic support to prevent future engagement in violent behaviour [16, 17]. As aggressive acts performed in mass violence are mostly found to be reward-driven , material rewards should reduce instrumentally used aggression. However, Theidon , who interviewed more than 100 former Colombian combatants, points out that, irrespective of the harsh reality, ‘militarized masculinity’ is one of the desirable rewards associated with a warrior’s life. Consequently, non-material rewards associated with combat, cannot be outweighed by money and might still arouse aggressive behaviour after demobilization. One further challenging issue is that there are two forms of demobilization in the Colombian demobilization process: On an individual level (mainly guerrilla fighters), as well as collective demobilization (mainly paramilitary forces). Correspondingly, there are former combatants who demobilized voluntarily because they were tired of fighting , while others just demobilized because of an agreement between the government and the forces’ leaders, without necessarily wanting to give up fighting. Combatants from both groups – paramilitary and guerrilla forces – tried to leave the force when they were tired of fighting, often because their lives were under threat. However, collective demobilization was primarily a consequence of negotiations between the government and the paramilitary.
With this study, we wanted to investigate whether appetitive aggression is still present among Colombian ex-combatants. We hypothesized that appetitive aggression would be prominent in those who were demobilized by force, as the attraction to violence would have contributed to their participation in armed groups. Moreover, because these combatants were not driven by intrinsic motivation to lay down their weapons, we tested the hypothesis that they would still be attracted to violence and benefit from the protective effects of appetitive aggression on traumatic stress. In contrast, we hypothesized that this effect would be weak or absent in those who demobilized individually and voluntarily. We expected them to no longer experience a protective effect of appetitive aggression. We assessed appetitive aggression in two groups of former combatants, one that was demobilized collectively by force and one in which the ex-combatants joined the demobilisation program on their own initiative. To test the first hypothesis, we compared appetitive aggression between these two groups. To investigate the relation between appetitive aggression and trauma load on the severity of PTSD symptoms, we calculated a moderation analysis.