What is connection between testosterone and aggression? The media loves to blame violence on “testosterone fueled aggression” but let’s examine this from a different angle.
The following is my (horrible attempt) summary from the book Behave: The Biology of Humans at Our Best and Worst by Robert Sapolsky. T is only a small part of the book, but one that I was most intrigued by.
At first glance it makes sense to hold T responsible as the cause of ferocity, as throughout the animal kingdom males are responsible for major acts of aggression. This aggression is especially amplified during periods of high testosterone namely puberty and mating season. Aggression increases T. But does T increase aggression? This is a very chicken- and- egg situation.
The first and simplest experiment would be to manipulate the presence, absence and then reintroduction of the variable into a system.
Manipulating some variables, we observe that castration leads to a decline in aggression but subsequent reintroduction of testosterone into that subject increases aggression. However, after castration, when no T remains, there is still some aggression. The more aggressive a male was before castration; the more aggression will remain after. For example, eunuchs played an important role in the Imperial Chinese military, prized for their fierceness. There are multiple other factors besides T, that play a role in aggression (namely the amygdala).
Testosterone and Confidence
Testosterone increases confidence and optimism while decreasing fear and anxiety (up to a certain point). This can be taken to an extreme, leading to overconfidence and narcissism. Impulsivity and risk taking is increased by decreasing activity in the prefrontal cortex and increasing the connection pathway between the amygdala and thalmus. Where as before, the prefrontal cortex controlled impulsive reasoning, its function is now suppressed.
It is important to note that the risk taking and impulsivity mentioned above can be both positive or negative. For example, “let’s gamble and invade the neighbouring tribe” or “lets gamble and make peace with the enemy.” Both situations are impulsive but only 1 is seen as aggressive. Rather than causing something, testosterone amplifies the power of something else to cause it, meaning that the effects of testosterone are clearly context dependent.
The feelings of overconfidence and grandeur from (high) T is pleasurable. An experiment showed that rats would willingly return to and press levers to be infused with more testosterone. In the brain, T increases neural sensitivity to dopamine (the feel-good chemical).
Testosterone and Competition
An increase in testosterone leads to aggression mainly in the presence of challenges or competitive pressure. After winning a competition, the ensuing release of T leads to an increase in glucose delivery and metabolism to the muscle cells, leading to pheromones that induce greater “fear” to those nearby. Additionally, following a challenge, an increase in testosterone is used to intensify behaviours that will maintain ones’ status. These behaviours could range from aggression to pleasantness.
If for the preservation of that status you are required to be “pleasant”, what happens? In an experiment, participants played a game where they would decide how to split a pot of money between themselves and another player. Those given testosterone before the experiment were more generous with their offers. In this scenario, maintaining status would require oneself to be sensitive to the social setting of the game, leading to this unlikely observation.
Where your pride rides on honesty, testosterone will decrease cheating. On the other hand, if violence is needed to maintain status, then aggression will be the tool used.
The actions of testosterone are purely context dependent.
The following is my (horrible attempt) summary from the book Behave: The Biology of Humans at Our Best and Worst by Robert Sapolsky. T is only a small part of the book, but one that I was most intrigued by.
At first glance it makes sense to hold T responsible as the cause of ferocity, as throughout the animal kingdom males are responsible for major acts of aggression. This aggression is especially amplified during periods of high testosterone namely puberty and mating season. Aggression increases T. But does T increase aggression? This is a very chicken- and- egg situation.
The first and simplest experiment would be to manipulate the presence, absence and then reintroduction of the variable into a system.
Manipulating some variables, we observe that castration leads to a decline in aggression but subsequent reintroduction of testosterone into that subject increases aggression. However, after castration, when no T remains, there is still some aggression. The more aggressive a male was before castration; the more aggression will remain after. For example, eunuchs played an important role in the Imperial Chinese military, prized for their fierceness. There are multiple other factors besides T, that play a role in aggression (namely the amygdala).
Testosterone and Confidence
Testosterone increases confidence and optimism while decreasing fear and anxiety (up to a certain point). This can be taken to an extreme, leading to overconfidence and narcissism. Impulsivity and risk taking is increased by decreasing activity in the prefrontal cortex and increasing the connection pathway between the amygdala and thalmus. Where as before, the prefrontal cortex controlled impulsive reasoning, its function is now suppressed.
It is important to note that the risk taking and impulsivity mentioned above can be both positive or negative. For example, “let’s gamble and invade the neighbouring tribe” or “lets gamble and make peace with the enemy.” Both situations are impulsive but only 1 is seen as aggressive. Rather than causing something, testosterone amplifies the power of something else to cause it, meaning that the effects of testosterone are clearly context dependent.
The feelings of overconfidence and grandeur from (high) T is pleasurable. An experiment showed that rats would willingly return to and press levers to be infused with more testosterone. In the brain, T increases neural sensitivity to dopamine (the feel-good chemical).
Testosterone and Competition
An increase in testosterone leads to aggression mainly in the presence of challenges or competitive pressure. After winning a competition, the ensuing release of T leads to an increase in glucose delivery and metabolism to the muscle cells, leading to pheromones that induce greater “fear” to those nearby. Additionally, following a challenge, an increase in testosterone is used to intensify behaviours that will maintain ones’ status. These behaviours could range from aggression to pleasantness.
If for the preservation of that status you are required to be “pleasant”, what happens? In an experiment, participants played a game where they would decide how to split a pot of money between themselves and another player. Those given testosterone before the experiment were more generous with their offers. In this scenario, maintaining status would require oneself to be sensitive to the social setting of the game, leading to this unlikely observation.
Where your pride rides on honesty, testosterone will decrease cheating. On the other hand, if violence is needed to maintain status, then aggression will be the tool used.
The actions of testosterone are purely context dependent.
