Neural and Hormonal Influences

• biological explanations argue that behaviour can be explained in terms of our biological make-up
• Gospic et al (2011) used the ultimatum game experiment to investigate the role of the amygdala. they used fMRI scans to see heightened responses in the amygdala when unfair offers were rejected. administering a benzodiazepine before playing a game reduces the activity in the amygdala and halved the number of rejections
• animal studies have been used to confirm the role of the amygdala in aggression.​ electrically stimulating the amygdala causes the animal to behave aggressively.​ removal of the amygdala prevents aggressive behaviour.
• the hippocampus plays a vital role in the formation of new memories. when encountering a threat animals compare the experience with prior experiences. This allows for the response behaviour to relevant to the current situation.​
• Boccardi et al. (2010) found evidence of hippocampal abnormalities in habitual violent offenders. 
• in normal levels serotonin is calming and inhibits the firing of the amygdala.​ low levels have been associated with impulsive and aggressive behaviours.​
• Mann et al (1990) administered questionnaires to assess levels of hostility and aggression.​ they gave 35 participants dexfenfluramine which depletes serotonin. ​they then re-administered the questionnaires and found that the males' scores increased.​
• Pardini et al (2014) found evidence that showed a correlation between reduced volume of the amygdala and a history if violence
• Rain et al (2004) found evidence that showed that a difference in symmetry of the hippocampus is linked to impulsive violent crime
• Hormones are chemicals that act as messengers that travel in the blood, stimulating organs and tissues to perform their respective functions
• Testosterone is a male sex hormone, which stimulates areas of the brain linked to aggression
• males are generally more aggressive than females. For this reason, theorists have focused on the male sex hormone testosterone
• Dabbs et al (1987) tested salivary testosterone of criminals and found that violent criminals had the highest levels of testosterone. This is evidence in support of high levels of testosterone being associated with aggression
• Dolan et al (2001) discovered a positive correlation between levels of testosterone and aggressive behaviour in human males using a sample of 60 prisoners in UK maximum security hospitals
• Manzur (1985) developed the biosocial model of status to explain the relationship between aggression and status. He argues that levels of testosterone fluctuate throughout the day. That is, biology is influenced by social action
• Mehta and Josephs (2006) did a study on testosterone changes with a sample of 64 male participants who provided two saliva samples. They provided the first sample before playing a game and the other 15 minutes after the game. The game was rigged so they’d always lose but were offered a rematch afterwards. 73% of participants whose testosterone increased did the rematch
• Carre and Mehta (2011) claimed that testosterone only leads to aggression when cortisol levels are low
• as most of the research is correlational it’s important that it’s testosterone levels may be a response to aggression and not a cause. therefore, a definitive cause and effect relationship can’t be established