There are some weaknesses with both of these studies. Wagner’s research used mice (animal research). Mice are not the same as humans so the results cannot be generalised to humans as humans are much more complex than mice and they may be other factors that may affect aggression in humans such situational factors that may cause a person to behave aggressively – this would be hard to test in mice as they are not on the same cognitive level as humans.
So therefore we cannot extrapolate these findings to humans as the mice may behave differently to humans when they have higher levels of testosterone. Harrison’s study only used male participants and then generalised the results to the whole population – these is beta bias, as it is assuming that there are no real differences between men and women. Also men have higher levels of testosterone than women – so how does it affect women?
Lenard suggested that serotonin was associated with over-eating, sleep, mood, impulsiveness, alcohol, abuse, depression and aggression. Most research seems to indicate that low levels of serotonin lead to high levels of aggression while high levels of serotonin lead to low levels of aggression. Davidson supports the neurotransmitter explanation of aggression because he consistently found lower levels of serotonin in criminals who were violent compared to those who were not. Further research into mice and monkeys whose serotonin 1B receptor was not functioning found that they were more aggressive than their healthier counterparts. Davidson’s study was good evidence to show that low levels of serotonin led to aggression because he consistently found the same results in humans and in monkeys which have similar genes to humans.
Overall the hormonal/neurotransmitter approach is similar to the genetic approach sit does not take into account other factors (e.g. social and cognitive factors). This makes it reductionist as it over-simplifies complex behaviour and ignores these factors. Therefore it would be hard to generalise the findings of the studies. It also suggests that our behaviour is determined by our hormones ignoring free-will. Humans have the ultimate choice in how they behave and react. This would make the explanation deterministic.
Brain structure can also play a part in aggression particularly when there is damage to the brain. Phineas Gage is an example of how damage to the brain can cause a individual to behave more aggressively. After an accident involving his head and a tamping iron, Phineas Gage went from being mild-mannered to showing very aggressive behaviour. This suggests that certain parts of the brain can alter aggression. However this is only true of one individual. Gage’s case was very unique in that in can never be replicated as it would obviously be unethical and also there will never be an exact case like it. So generalising the findings would be very limited.
In conclusion, the biological explanation seems to have a high emphasis on nature and focuses mainly on the biological factors that may cause aggression. Aggression can not be caused by biological factors alone, there must be other influences and explanations as to what causes aggression. The explanation ignores these making it reductionist. It could include psychodynamic causes, social and environmental and also cognitive explanations to further improve on the explanation. Also aggression can not just be put down to one cause – even if a person has high levels of testosterone and low levels of serotonin it does not mean that they are going to behave aggressively. Aggression may also depend on situations and events that occur so it cannot only be put it all down to biological influences.