Neural and hormonal influences Biochemical influences on aggression

Remind Yourself How many neurotransmitters can you remember? How to they work? Which is the master gland? How do hormones operate? Which parts of the brain are involved in aggression? Can you spell them?

Neural Influences Serotonin: generally has an inhibitory effect, therefore low levels can be linked to aggression. This is particularly true if the brain area associated with the control of aggression has low levels of serotonin Dopamine: an excitory neurotransmitter which has been associated with high levels of aggression. The amygdala: responsible for quickly evaluating the emotional importance of sensory information. It works in conjunction with the thalamus, hypothalamus and hippocampus (together known as the limbic system) and may respond with aggression, fear or relaxation.

Hormonal Influences Testosterone: high levels of this male hormone are linked to aggression. Male levels peak at around 18 -21. There is much correlational evidence for a connection between testosterone and violent behaviour. Cortisol has also been implicated but the connection is unclear and there are contradictory studies. Oestrogen and oxytocin are both implicated in the reduction of aggression but again there are conflicting research studies (oxytocin has been shown to increase lying to defend in-group members – Carlsten De Drue)

Supporting research Testosterone and aggression. Levels reach a peak in young male adults and decline with age. Pope 2000: double blind procedure. One group given testosterone the other a placebo – p’s had to push button to reduce amount of money paired participant received – testosterone group pushed button significantly more frequently. Evaluation: Controlled conditions above, however the nature of the task can be criticised. In general, although testosterone is involved in aggression it is not a causal relationship; it just makes aggression more likely.

Supporting research Dopamine and aggression. Link not as well established as with serotonin. Lavine – 1989 – amphetamines increases dopamine and is linked with aggressive behaviour. Couppis – individuals seek aggressive situations because of the dopamine rush. Evaluation: difficult to research as dopamine has many other functions e. g. ability to move. Schizophrenics have high levels of dopamine.

Supporting research Duke 2013 found a small inverse relationship between serotonin levels and aggression. Pardini 2014 found reduced amygdala volume correlated with higher levels of aggression, suggesting poorer ability to process emotionally sensitive information. Raine 2004 identified a link between impulsive behaviour in violent offenders and asymmetry in the hippocampus, suggesting a failure of the hippocampal, amygdala axis. Note: three to four studies will be sufficient – of which one must be for testosterone; one for serotonin and one for the limbic system

Correlations Spell it out: significant of numbers of males without high levels of …………. . are aggressive; and many males with high levels of ………………. are not aggressive. The same is true of the serotonin studies. There is no causal link in humans. Clearly other variables are implicated, such as ………………. and………… Neuro transmitters like serotonin are implicated in many other behaviours and moods, such as …………………and………… Therefore, it is difficult to manipulate serotonin without potentially undesirable side effects.

Specific Issues Aggression or status seeking? Eisenegger found that testosterone can make women “nicer” (depending on the situation), suggesting that aggression may be just one type of status seeking. Gender: What no oestrogen? Jenny English and premenstrual tension. Alpha bias – ignoring SLT influences and rise of female violence – or at least the rise in the reports of female violence (ONS) Research e. g. Mc. Burnett, conducted almost uniformly on males. More research needed into both neural and hormonal effects on female aggression. Culture: Margaret Mead and the !kung San people.

So What? Other approaches emphasise the importance of the environment (SLT) and cognitive control structures while stressing the importance of freewill and self control (Cognitive). Alpha bias in Biological theories tends to exaggerate the gender differences, while current research shows sharp increases in female violence (UK), both domestically and publically. Mechanisms of state may suppress uncomfortable findings – publisher bias. Interactionist explanations offer the most realistic explanations although severe biological imbalances may be difficult for any individual to counteract. The important question (1): What has been my theme? Repeat it here…. . The important question (2): Given that experts in the field warn against reductionist conclusions, why do so many psychologists seek them?