Testosterone Research

Testosterone Psychology Definition: Testosterone Function

To understand how testosterone is linked to aggression, we must first establish what testosterone is. Many believe it is a purely masculine hormone, however, this is not necessarily the case.

Hormones act as chemical messengers in the body, stimulating various cells and tissues depending on the reason behind the testosterone secretion.

The hypothalamus regulates testosterone production in the brain, and the pituitary gland acts as the overseer of the gonads and adrenal glands.

Testosterone also enables secondary ‘male’ characteristics, such as muscle and skeletal growth, as well as body hair and facial hair. These characteristics tend to be less developed when there is not enough testosterone in the body of males undergoing puberty.

Testosterone Psychology Example

Testosterone is one of the main driving forces behind the actualisation of aggressive behaviours in psychology (Batrinos, 2012). These can manifest as, or through:

• Anger (thoughts, feelings).

• Verbal aggressiveness.

• Dominance.

• Competitiveness.

• Physical aggression.

Amongst other examples. Testosterone in psychology mainly revolves around aggression and the development of male characteristics.

Testosterone and Aggression: Psychology

How are testosterone and aggression linked? Well, fluctuating levels of testosterone can have various effects on the body and brain. Testosterone is also closely linked with the brain regions associated with how aggressive behaviours come about—namely, the amygdala.

Testosterone activates the amygdala, enhancing its resistance to regulation from the prefrontal cortex (PFC), and increasing its emotional reaction to stimuli (Batrinos, 2012). Thus, when something threatening comes along and stimulates the amygdala, the person will have an emotional response.

High testosterone levels mean that the areas of the brain that usually ‘calm down’ the amygdala if the threat is not as serious as once thought, are no longer as effective. As a result, emotions run higher and aggressive behaviours increase.

Usually, testosterone is mediated by different brain regions, as well as cortisol and serotonin. In healthy, normal levels, aggression occurs and is mediated correctly, so people can react appropriately to different situations. Without this mediation, aggressive behaviours are more likely to occur.

High levels of testosterone are linked to dominant, and often times aggressive, behaviours.

Fig. 2: Testosterone affects the amygdala.

Mazur (1995)

In this study, researchers measured 4,179 Vietnam veterans’ hormone levels (testosterone, cortisol, and thyroxine). Hormone levels varied with the veterans' age, social status, and race, and interestingly, all three of the aforementioned hormones were related to deviant behaviour.

Mazur and Michalek (1998)

In this study, male air force veterans who were going through a divorce had higher levels of testosterone compared with those who were currently married. This suggested that testosterone levels are not constant. They vary depending on a person’s social standing and context.

They also suggested low testosterone levels in married men could explain low criminality rates amongst married men, and how rising levels of testosterone that occur leading up to a divorce may explain increased levels of abuse towards the wives.

Psychological Effects of Testosterone: Evaluation

Considering the above, it’s important to evaluate the studies and research surrounding testosterone and its association with aggression.

Kreuz and Rose (1972)

In this study, they measured the testosterone levels of 21 young, white male prisoners who had a history of aggressive

behaviour, and who had displayed aggression whilst in prison.

They tested the participants using the Buss-Durkee Hostility Inventory, the Marlowe-Crowne Social Desirability Scale, and the Institute for Personality and Ability Testing Anxiety Scale Questionnaire.

• Researchers found that of the 10 participants who had committed violent crimes or had a history of aggressive behaviours had higher levels of testosterone compared to the 11 participants who didn’t have this history.

The results suggest that higher levels of testosterone are related to aggressive or violent behaviours, supporting the argument for high testosterone levels linking to aggression. The sample size for this study was low, however, reducing its generalisability. Considering how the study was conducted on violent prisoners, generalisability is lowered even further, as it's not applicable to the public.

Dabbs et al. (1987)

Dabbs et al. (1987) measured the testosterone levels in the saliva of 89 prisoners.

• Researchers found that nine out of 11 inmates with low testosterone levels had committed nonviolent crimes in the past. When we compare this to prisoners with high levels of testosterone, we find startling differences. 10 out of 11 inmates with the highest testosterone levels had committed violent crimes in the past.

The results suggest again that high levels of testosterone are linked to more aggressive or violent behaviours, even when associated with crime. This study, as well as Kreuz and Rose’s, has a relatively low sample size and is quite specific as it focuses on prisoners, affecting generalisability.

Mazur (1985)

In his analysis of aggression and dominance, Mazur found that high testosterone levels are directly related to dominant behaviours, specifically, aggressive behaviours. Criminals and those involved in military professions who had high levels of aggression were found to also have high levels of testosterone.

However, this does not mean high levels of testosterone result in aggression every time. Mediating factors, such as social contexts and the individual levels of control, especially when we consider serotonin and cortisol, affect how these aggressive behaviours manifest.

Mazur suggested that there isn’t a completely causal relationship, either. Testosterone is associated with aggressive behaviours, but we can’t say that it’s the direct and only cause, it is only correlational.

Wagner et al. (1979)

In this study, Wagner et al. (1979) analysed the effects of varying hormone levels on biting behaviours (aggressive behaviours) in mice. They referred to these as bite-attack levels.

• Castration affected hormones in male mice and the bite-attack levels lowered upon castration. However, these mice showed an increase in bite-attack levels after being injected with testosterone to regain normal hormonal levels.

The results show that testosterone is important in the expression of aggressive behaviours in male mice and is critical for bite-attack behaviours. Some suggest this study is a good model for studying pharmacological and physiological effects on aggressive behaviours.

Motta et al. (2018)

Motta et al. (2018) investigated testosterone treatment and anger expression in transmen. They assessed 52 transmen diagnosed with gender dysphoria through questionnaires (self-report)

Over seven months of gender-affirming hormonal treatment, anger expression and arousal control increased in transmen. They found that psychological support can help reduce angry behaviours and overall help with transitioning.

Correlation versus Causation: Van Goozen et al. (1995)

A lot of research tends to suggest there is a correlation between high levels of testosterone and higher levels of aggression, but they struggle to identify a causal link. We cannot conclusively say, for instance, in Dabbs et al. (1987), that high levels of testosterone caused more aggressive behaviours.

Van Goozen et al. (1995) investigated how aggression levels changed in transsexuals, both male-to-female and female-to-male, and provided more ground for cause and effect. The study included 35 female-to-male participants and 15 male-to-female participants.

• They found that those transitioning from female to male had higher levels of aggression (through self-reported data) after they began hormone therapy (testosterone), including increased levels of aggression proneness, sexual arousability and spatial ability performance.
• Male-to-female participants reported lower levels of aggression after taking anti-androgens, showing decreased levels of anger and aggression proneness, sexual arousability and spatial ability decreases.

Self-report data is a weakness of the study, however, as although experimental manipulation increases the evidence for cause and effect, self-report data is prone to subjectiveness and not always reliable.