Testosterone And Amygdala

A major biological influence on behaviour are hormones. Chemical messengers that spark physical reactions throughout the body from the activation of glands in the endocrine system.

Linked with the manifestation of aggressive behaviour, the hormone testosterone affects human behaviour through the stimulation of the amygdala, which activates the hypothalamus and pumps adrenaline into the body, thus resulting in emotional and physical preparation for confrontation.

This is evidenced by Radke et al. (2015) who aimed to investigate the effect of testosterone on the amygdala and the prefrontal cortices in 54 healthy females. Their findings substantiates, that higher levels of testosterone causes more activity in the amygdala approaching angry

(2015), who, similarly, investigated the effect of testosterone on the function of the amygdala. Their procedure included giving 16 healthy young men doses of testosterone, and four weeks later giving them a placebo. Simultaneously, as the men were viewing images of facial expressions (neutral,sad, angry, happy) their brains were scanned by an fMRI machine.

Their findings showed that participants injected with testosterone, presented increased reactivity (meaning the level of activity in the brain as it is reacting to a stimulus) in the amygdala and the hypothalamus when they were viewing the angry faces. In contrast, testosterone didn’t have the same influence if they were observing other emotions.

The study fortifies the amygdala’s role in social threat perception as well as the hypothalamus’ responsibility in the release of adrenaline during a fight or flight response. Moreover, it shows how the amygdala isn’t solely involved in the perception of a threat, but also motivation to deal with it. The study doesn’t give a clear view on how this activation of the amygdala leads to acting in a violent way, however, it indicates that testosterone would cause aggressive behavioural changes because the body is preparing for

Zak et al. (2009) aimed to investigate the effect of testosterone on male aggressiveness, the researchers used a sample of 25 male students, measured their baseline levels of testosterone before rubbing a gel with testosterone or placebo onto one of their shoulders. After 24 hours, the participants had their blood taken to record the new testosterone level.

Subsequently, they were asked to play the ‘Ultimatum game’; each participant had explained to them that they could be generous by give a larger amount of money to another player, or be tight-fisted with their money. Offers that were too stingy could be rejected, causing both players to lose their money. This was a counterbalanced repeated measures design and the experiment was repeated again after four weeks (using the other shoulder of the participants).

They found participants had been 27% stingier when they received testosterone gel, than with the placebo. Therefore indicating that men with higher levels of testosterone would be more selfish and more likely to punish others, further linking testosterone with aggressive