Aggression

Biological Explanations of Aggression

Neural Mechanisms

• The Limbic System: Located in the middle of the brain, the limbic system controls emotional behaviours like mood.
• The Amygdala: It perceives emotional responses such as anger from others, assesses and responds to potential threats. A highly responsive amygdala leads to the perception of more threats and an increased likelihood of aggression.
• The Hypothalamus: This region inhibits aggressive responses. Structural abnormalities in the hypothalamus can impair its functioning and lead to increased aggression.

Analysis of Neural Mechanisms

Positive Evidence:

• Gospic et al. used the ultimatum game to show that participants who perceived social provocation and rejected unfair financial splits exhibited fast and heightened activity in the amygdala. Benzodiazepine, which lowered amygdala activity, also halved the number of rejections.
• Bard & Mountcastle’s research supports the regulatory role of the hypothalamus in aggression. They found that separating the cortex from the limbic system and damaging part of the hypothalamus in cats increased aggression, suggesting the hypothalamus regulates violent behaviours.

Criticisms:

• The model is considered overly simplistic. Coccaro et al. highlighted that the orbitofrontal cortex (OFC) also plays a critical role in regulating impulses, and disruptions here can lead to heightened aggression. This suggests that a broader neural network involving the limbic system, OFC, and additional factors like hormones and neurotransmitters needs to be considered.

Serotonin

• Serotonin generally inhibits neural activity, which slows communication between neurons, helping individuals remain calm and maintain a stable mood. However, lowered levels of serotonin increase the firing of OFC neurons, leading to increased aggression because impulses from the amygdala are not adequately dampened.

Analysis of Serotonin’s Role

Supportive Evidence:

• Virkkunen et al. found that the metabolite 5-HIAA, a serotonin waste product, was significantly lower in the cerebrospinal fluid of violent impulsive offenders compared to non-impulsive offenders, suggesting a link between low serotonin levels and impulsive aggression.
• Berman et al. conducted a study where participants given paroxetine, which increases serotonin activity, gave fewer and less intense electric shocks compared to those given a placebo, under similar provocation levels.

Criticisms:

• Research has been criticised for primarily showing correlations rather than causation, although Berman et al.’s study suggests that increasing serotonin can reduce aggression.
• Gender bias is evident in studies such as those by Mann et al., where only male participants reported increased aggression after intake of dexfenfluramine, a drug known to reduce serotonin levels, indicating that findings might not be universally applicable across genders.

Hormonal Mechanisms

• Testosterone: An androgen hormone, testosterone has been correlated with higher aggression. It acts on serotonergic synapses and lowers serotonin levels, thus reducing the inhibition of aggressive impulses from the limbic system.

Analysis of Testosterone

Supportive Evidence:

• Animal studies by Wagner et al. and Simpson found that castration reduces aggression in male mice, and testosterone injections restored aggression to pre-castration levels.
• Human research by Dolan et al. found a positive correlation between high testosterone levels and aggressive behaviour in offenders in maximum-security hospitals.

Criticisms:

• The direction of the relationship might be incorrect. Sapolsky noted that higher aggression could produce higher testosterone levels, rather than the other way around.
• Klinesmith et al. found that handling a gun increased testosterone levels and aggressive behaviour in participants, suggesting that environmental stimuli can also increase testosterone and aggression.

Genetic Factors

• MAOA Gene (Warrior Gene): Aggression is likely influenced by multiple genes, but the MAOA gene is a notable example. This gene regulates the production of the MAOA enzyme, which breaks down neurotransmitters like dopamine, noradrenaline, and serotonin. Variants of this gene affect aggression levels.

Analysis of Genetic Factors

Supportive Evidence:

Research by Mattson and Godar et al. selectively bred mice with the MAOA variant to show increased aggression. Coccaro et al.’s twin studies found significant concordance rates for physical and verbal aggression in monozygotic twins compared to dizygotic twins.

Criticisms:

• Animal studies may not directly apply to humans due to complexities in human genetics.
• Twin studies are often criticised for assumptions about the environment and genetic interactions, such as treating dizygotic twins differently or the possibility that they share more than 50% DNA.
• The interactionist approach, supported by Caspi et al. and Frazzetto et al., suggests that both high and low activity variants of the MAOA gene can lead to aggression, but typically only in conjunction with environmental factors like early trauma.

Media Influences on Aggression

Cognitive Priming

• Cognitive Priming: This mental process involves learning scripts or schemas on how to behave aggressively in specific situations, which are automatically retrieved when triggered by environmental cues. Exposure to violent media such as films, TV, and computer games (Huesmann et al.) enhances the learning of these aggressive scripts.
• Impact: Exposure to violent media increases violent thoughts and ideas, boosting motivation to act aggressively, a process known as priming (Berkowitz). For example, in video games like GTA, aggressive driving behaviours in the game can influence real-life driving behaviour when similar environmental cues are present.

Analysis of Cognitive Priming

Supportive Evidence:

• Bushman’s study demonstrated that exposure to violent films significantly increased participants’ sensitivity to aggressive words compared to those who watched non-aggressive films, illustrating the priming effect.

Criticism:

• Laboratory experiments, including those on cognitive priming, often lack mundane realism, questioning the applicability of findings to real-world settings. The effects observed in lab settings may not translate into long-term behavioural changes outside the lab.

Desensitisation

• Desensitisation: Repeated exposure to violent media content leads to decreased physiological arousal responses to aggression, making such behaviour seem more acceptable and likely to be imitated. Viewers become less sympathetic to victims and less likely to perceive aggression in real life.
• Example: Players of “Call of Duty” become accustomed to and less emotionally affected by violent actions within the game, potentially influencing their reactions to real-life violence.

Analysis of Desensitisation

Supportive Evidence:

Studies like those by Weisz & Earls and Krahe et al. show that exposure to violent media results in lower physiological arousal (e.g., skin conductivity) and reduced empathy towards victims, as illustrated by participants’ reactions in simulated court cases and noise-blasting tasks.

Criticism:

The long-term effects of desensitisation are still debated. Critics argue that the immediate reductions in arousal observed in laboratory settings may not persist, and other factors like individual differences and context might influence the impact of violent media.

Disinhibition

• Disinhibition: Exposure to media violence can weaken the social norms that usually inhibit aggressive behaviours, making such behaviours appear more acceptable and likely to be enacted. This phenomenon is particularly pronounced immediately after exposure when physiological arousal can prompt aggressive responses.
• Impact: Over time, repeated exposure to violent media can permanently reduce inhibitions towards aggression, as the behaviour is normalised through media portrayal.

Analysis of Disinhibition

Supportive Evidence:

• Berkowitz & Alioto found that participants exposed to films where aggression was portrayed as justifiable vengeance were more likely to administer longer, more intense electric shocks to others, indicating that media can normalise and encourage aggressive responses.

Criticism:

• Disinhibition effects, like other media influence theories, may be overly simplistic. Research often fails to account for individual variability and the complexity of interactions between biological predispositions and environmental influences.

Overall Analysis of Media Influences on Aggression

Weight of Evidence:

• Bartholow and Anderson’s experiment demonstrated that participants who played violent video games like “Mortal Kombat” exhibited higher levels of aggression in laboratory tasks compared to those who played non-violent games, suggesting a causal link between media violence and aggressive behaviour.

Research Limitations:

• Laboratory settings often lack the complexity of real-world environments, and the effects observed may not fully represent the dynamics of media influence over time.
• Critics, including Ferguson et al., argue that when other variables such as trait aggression, family violence, and mental health are considered, the impact of violent media on aggression diminishes, indicating that aggression is influenced by a broader range of factors than media exposure alone.

Simplistic Explanations:

• The impact of media on aggression might be oversimplified in many studies, neglecting the role of individual differences and genetic factors, which could make some individuals more susceptible to media influences on aggression than others. This complexity suggests that the relationship between media exposure and real-life aggression may be more nuanced than currently portrayed in research.