Does Taking Testosterone make you Mean?

Does Taking Testosterone make you Mean?

Written by Ben Bunting: BA, PGCert. (Sport & Exercise Nutrition) // British Army Physical Training Instructor // S&C Coach.


The role of testosterone has long been debated in the male population. The hormone testosterone, which is produced in men's testicles and a smaller amount by female ovaries, has been associated with male characteristics for a long time. 

You can imagine that the answers to questions about testosterone and masculine behaviors are not simple. Before testosterone is put under the spotlight it's important to note that any hormonal effect on behavior can be debated until your blue in the eye. 

Initially, testosterone is often associated with cheating or bodybuilders whose sole goal is to build up muscle, increase energy and/or boost confidence. The "male hormone", also known as testosterone, is closely linked to sexual drive and a general perception of'manliness.

Long ago, testosterone was associated with a variety of male-typical behaviors. The review highlights the key aspects of behavioural endocrinology and provides a summary of research on testosterone-related male behaviors. Some evidence in support of the assumption is found, but some critical issues regarding testosterone-behaviour relationships are also raised.

When you think about testosterone, you may associate it with lust and violence. In fact, testosterone has been dubbed 'the hormone of aggression' because it is associated with negative and antisocial traits, primarily male.

In the last decade, our main research has investigated whether testosterone levels can be related to certain masculine behaviours. The answer, as you would expect, is not simple. 

One thing to note is that hormones don't directly affect behaviour. They influence it when it occurs in the appropriate social/environmental context. Researchers who are trying to determine hormone-behaviour relations face a challenge in identifying the environmental/social factors that may be relevant.

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Human and Hormone Development 

Animal models are used routinely in behavioural endocrinology to answer such questions. In behavioural endocrinology, the effects of hormones are usually described as 'organisational effects' or 'activational effects'. 

It is well known that testosterone levels during early development of the fetus play an important role in the differentiation between sexes. 

In the beginning, the sexes are undifferentiated. The presence of TDF (Testis Determining factor) on the male Y-chromosome triggers massive testosterone secretion by the testes. 

The body and brain are shaped in a masculine direction and female development is suppressed. The absence of the protein causes the development of the nervous system and body to proceed in accordance with nature's default settings (female) when it is absent from the female fetus. 

Later, in puberty, and even beyond, the second "activational" effect is evident: cells and tissues that were initially arranged along male-female lines are subsequently 'activated by sex steroid hormones (Nelson 2000). 

To compare the organisational and activational effects of sex steroids, animal models are used. For example, castrating males before or following fetal sexual development, or before or following pubertal maturation. 

These males are compared to other males that have not been castrated. They can also be compared in terms of their physical and behavioral characteristics with males left intact. 

These studies provide important information about the effects of sex steroid on certain animal behaviors. It is more challenging to assess the hormonal environments associated with human development, and compare them to subsequent behavior in humans. 

It is impossible to conduct castration or replacement experiments due to ethical reasons, but certain clinical conditions where the fetus was exposed abnormally high levels of hormones may shed light on this topic. 

Congenital Adrenal Hyperplasia is a condition where the female fetus has been exposed to high testosterone levels, which act to masculinize her external genitalia. 

Psychologists find it more interesting that girls with CAH exhibit more masculine behaviours such as increased rough and tumble play, aggression and toy preference. (Berenbaum & Hines, 1992).

Finger Digit Ratio

Psychologists seemed to have difficulty determining the organisational effects of sex steroid use in groups that were not clinical. Anatomical observations of the hands made over a hundred years ago may have given a window on prenatal exposure to steroids.

Researchers have noted the sexual dimorphism of the difference between the lengths of the index and ring fingers.

In males, the fourth finger tends to be longer while for females they are usually about the same. This difference was not easily explained at the time and remained a fascinating scientific sidenote.

That is, until John Manning published his book Digit Ratio in 2002. Manning suggested that estrogen and testosterone prenatally affect the finger growth in a differential way. We don't yet know why the second and fourth fingertips are so sensitive to early hormones.

The male fetus, who is usually exposed to higher testosterone levels, has a larger fourth finger than their second. 

The difference between the second (2D), and fourth (4D) finger can be easily measured with calipers. This 2D:4D (lower for males and higher for females) ratio correlates to various physical and behavioral traits.

We have investigated these relationships with various collaborators and found interesting associations between 2D/4D and the following: numerical processing (Brookes, et. al. 2007), personality traits (Fink, et. al. 2004a, 2006), body morphology and hand skills (Fink, et. al. 2004b), perceptions of masculinity and dominance (Neave, et. al. 2003). 

Researchers have found significant correlations between the 2D/4D ratio and aggression measures (Bailey & Hurd 2005), sex identity (Rammsayer & Trche 2007), sexuality (Rahman 2005), sporting achievements (Tester & Campbell 2007) and SAT test performance (Brosnan 2008).

Any observed relationship is only circumstantial. Evidence relies on associations between traits that depend upon sex steroid use.

Correlations do not necessarily guarantee causation. Even though measuring two fingers may be the best way to estimate prenatal exposure to steroids (McIntyre 2006), it will only provide information on a small window of development in early pregnancy (Putz and colleagues, 2004). 

Many researchers are now using this simple technique, and many papers reporting associations between 2D:4D and various behaviours/characteristics have now been published; large-scale meta-analytic studies will hopefully inform us as to the reliability and validity of these many reported associations.

RELATED: Read more about finger length and testosterone, here.

Steroid Hormone Activation

It is now easier to answer research questions about the activational effect of testosterone because measuring levels of testosterone circulating and comparing them with observed behaviors are relatively simple. 

The bioavailable or 'free testosterone' can be determined in the saliva as well as blood, and this testing can take place outside of laboratory settings in different groups. children, athletes, etc.) 

There are several research paradigms that can be used. Most commonly, correlational research is used - comparing testosterone levels with certain behavioral characteristics. 

There are also more experimental designs that can be used, such as comparing testosterone levels between groups or within individuals under different circumstances. 

Home advantage is a phenomenon that occurs in many sports. Teams win more matches and score more points when they play at home. 

Home advantage has been explained by referee bias and home crowd support. The home team is more familiar with the venue, the team at home knows it better, the team away from home experiences, less travel fatigue, etc.

Another factor could be physiological and relate to the perception of territoriality. Animals display territorial behavior (fighting), which is mediated at least in part by testosterone surges (Wingfield, et. al. 1990). 

Could a spike in testosterone prior to defending one’s own territory explain home advantage, as humans display similar territorial behaviour? 

In two studies, Neave & Wolfson (2003) found that there is a surge in testosterone before a football match at home compared to a game away or a practice session.

This surge was more pronounced when the team playing against a supposedly 'bitter rival'. We can't say for sure how testosterone improves home-player performance.

But likely explanations include increased motivation, improved confidence, faster reaction times, better information processing and greater physiological capacity. 

We also need to find out how testosterone levels differ between individuals and their performance in a match. And if it's possible to manipulate testosterone (legally), to boost team performance while playing abroad. We continue to research these questions.


For some time, the association between testosterone and aggression has attracted considerable attention (e.g. Archer, 1991; O'Connor et al., 2004; Pagonis et al., 2006). 

It has been caused by a number of developments. First, there was the media attention given to incidents of "roid rage" that appeared linked with abuse of AAS by athletes. 

Second, exogenous testosterone is used clinically to develop a hormonal contraceptive that can be reversed for men. It's also used as a replacement therapy for HIV and in treating men with age-related psychological and physical effects.

Early correlational data and anecdotal evidence suggest that testosterone levels in men increase male-typical behaviors, like physical aggression, persistence and anger. 

Most of the research is observational, retroactive and/or trans-sectional. This makes it hard to draw conclusions on causal relationships between testosterone and masculine behaviour.

Researchers have recently focused on conducting experiments where the testosterone level can be controlled. 

In the studies that have already been conducted, testosterone has been given in different dosages for various purposes. 

Some studies, for example, have used high supraphysiological testosterone doses to simulate the levels of AAS users. Some studies, such as those involving hormonal male contraception or testosterone replacement, have used a therapeutic dosage that is lower than the recommended level. 

The differences in method complicate the conclusions made about how testosterone affects important male behavior.

A recent review compared testosterone administered at supraphysiological and therapeutic levels to the effect on men's aggression, anger, and mood (O’Connor, 2007). 

Results showed some evidence of an association between supraphysiological testosterone doses and increases in direct measures of aggression, anger and emotion. 

The studies which administered the highest doses showed that a significant but small number of patients experienced psychiatric symptoms such as manic episodes following treatment. (Su, et. al. 1993). 

The therapeutic dose studies, which used a variety of measures reported by the participants and their partners, showed little to no change in mood or aggression outcomes. O'Connor et al., 2004).

Together, these findings suggest that testosterone doses used for medical purposes do not cause changes in aggression or anger. 

The reports that AAS users exhibit high levels of aggression and experience episodes of hypomania or mania following massive doses should not be extrapolated or compared to therapeutic testosterone doses.

The current research suggests that testosterone is not linearly related to aggressive behavior. There seems to be an upper limit to which the exogenous injection of high levels of testosterone can cause negative behaviours in certain people. 

These effects are likely to be moderated by individual differences in traits like impulsivity (see O’Connor et. al.,2002). Further studies with more complex designs, more sensitive measures, and reports from partners are needed to identify important vulnerabilities (O'Connor, et. al. 2001b). 

It is also necessary to determine whether or not the low incidence of psychotic symptoms among illicit AAS users is an accurate estimate, or if the results of only a few studies are just the tip of the Iceberg.

Sexual Behavior

The role of testosterone in sexual behavior in humans is well-established. The first behavioral evidence came from the studies on hypogonadal males who have low testosterone levels or none at all due to their abnormal gonadal functions.

As a consequence, they exhibit impaired sexual function.

These men's sexual functions are restored once they receive testosterone replacement therapy (Wang, et. al.,2000).

Can increases in testosterone circulating activate changes in sexual functions, like sexual behavior and libido, for example? 

It is important to ask this question, given the likely future adoption of male hormonal contraceptives by sexually active men. Numerous previous studies failed to detect any "negative" effects of testosterone exogenous on sexual behavior, even though it was suggested that the measures used were insufficiently sensitive and detailed. 

Bagatell et al., (1994). A cross-over, comprehensive study, conducted double-blind and placebo-controlled (O'Connor et. al., 2004,) found that increasing testosterone in young healthy men didn't increase the inter-actional (i.e. In a comprehensive, double-blind, placebo-controlled crossover study (O'Connor et al. 2004), increasing testosterone levels in healthy young men did not significantly increase either the interactional (i.e. The libido component of sexual behavior).

These findings could be explained by the fact that relationships and social factors are more important than sexual activities. 

Some data show that testosterone administered in therapeutic doses can increase sexual arousal under controlled laboratory conditions, using a dichotic hearing task. (Alexander and al. 1997). 

The majority of the evidence shows that testosterone treatment reliably restores normal sexual function in men who have lower testosterone levels than usual.

When hormone levels rise above normal, they can have an impact on the interactional and non-interactional aspects of sexual behavior. 

As part of the European Male Ageing Study, we have turned our focus to the relationship between declining hormone levels and a variety of behavioural outcomes among ageing males.

Cognitive Function

The hormone administration studies also provide useful insight into factors that are associated with cognitive performance variations, especially in relation to established gender differences in cognitive function. 

Men are known to perform better on visual-spatial tasks than women, and women do a better job on perceptual speed and verbal fluency tasks. 

It is also important to recognize that men and women perform similarly on these tasks, despite the fact the differences in mean performance are much smaller. 

These differences can be explained by a number of biologically plausible explanations. There is evidence that the endogenous sexual hormones can affect cognition through their pre- and postnatal effects of sexually dimorphic structures in the brain (Collaer, Hines 1995). 

In a landmark study Hier and Crowley (1982) showed that men with low androgen levels, or hypogonadals, had a significant deficit in their visuospatial abilities compared to matched control men and men who developed the condition after puberty. 

This indicates that testosterone can have an organizational effect on normal spatial abilities. We found that testosterone also has activational effects in cognitive function in healthy men.

Improvements in verbal abilities were associated with a decrease in spatial ability after testosterone treatment. 

The findings indicate that there is no clear relationship between cognitive function and testosterone, but that a certain level of the hormone is necessary for normal spatial abilities.

The decline of cognitive ability is associated with age-related testosterone reductions. 

In fact, a number of studies examined the possibility that testosterone supplements for older men could improve cognition. 

Recent research has shown that testosterone replacement therapy for men may have positive effects on cognitive function. 

Cherrier and co-workers (2007) discovered that testosterone increases of moderate to high levels were linked with improvements in spatial and verbal memory. 

Future research could explore this promising area, which may have implications in treating men who already suffer from cognitive problems such as Alzheimer's or mild cognitive impairment.

Testosterone and Human Development

The levels of sexual steroids are the main difference between the two sexes during fetal growth. 

The Y-chromosome triggers the production of the hormone in testes in men, even though women have only a tiny amount. The body and the mind suppresses female-typical growth, instead forming in male-typical directions. 

What is the importance of testosterone? Without its involvement during the development of a baby, it would form with nature's default gender - female. This also answers the question 'why men have nipples'. You are welcome. 

The impact of testosterone on fetal growth is not as noticeable during the puberty stage. The peak of sexual maturity occurs in the late teens of a male, and higher testosterone levels are observed.

This is accompanied by a deepening of voice, increased facial hair, as well as other hormonal changes, including morning erections. 

Social Status

Researchers have long compared men and women to their animal counterparts for hormones, behaviors, or the effect of castration. However, there are some differences. 

The results of human studies are not as promising, despite the fact that these animal studies have examined testosterone levels and aggressive behavior. 

The levels of testosterone are not consistent among people, which makes it difficult to determine the effects. They can fluctuate according to many factors, including age, health and time of the day. 

So, does testosterone cause aggression? What other effects does testosterone have on the mind? 

Researchers have focused on the relationship between testosterone and mood for some time. Studies have shown that testosterone, despite its association with antisocial or aggressive behaviours, actually increases the desire for a higher social status. 

Research on animals and testosterone has drawn comparisons with men's soccer, in particular home matches and the surge of testosterone that occurs when thinking about 'protecting home territory'. 

This study also suggests that testosterone increases when players defend their home grounds, increasing motivation and player confidence. It's obvious when you stop to think about it. You may have attended home games and noticed that the crowd's support alone can motivate a team. 

Role of testosterone in Males

The male hormone testosterone is extremely important for many reasons. Testosterone begins to help form male genitals around seven weeks after conception. As men grow older, their testosterone levels fluctuate, which can lead to hair growth, an increased voice, more muscle and more energy. 

A man's body sends signals to the system that controls testosterone via chemicals and hormones released in his bloodstream. The hypothalamus in the brain tells the pituitary how much testosterone to release before it is sent on to the testicles. 

Although the research is inconclusive, researchers continue to doubt testosterone's influence on personality traits such as aggression and mood. T- levels hava been associated with a competitive spirit and boosted self-esteem. 

Testosterone levels increase during puberty and along with these changes, the sexual desire also grows. A man who has lower testosterone levels may experience erectile problems and a drop in libido. 

The testosterone is responsible for the difference in sexual desire between men and women. 

Studies show that testosterone levels also affect metabolic functions, bone, and muscle maintenance. 

Each year, testosterone levels begin to decrease after the age 30. If you notice a sudden increase in testosterone, you should consult your doctor. 


Like any other hormone, testosterone can affect mood and personality. 

Discussions about the relationship between testosterone, human behavior and animal behavior are common. Comparisons between humans and animals have been made. 

Low testosterone is a common cause of low libido and other issues. However, this doesn't need to be the case. 

There is still a lot of work to be done in order to fully understand the relationship between testosterone and behaviour. 

The traditional research questions focused on testosterone's role in male behavior. However, we now realize that it is not a linear relationship. We are also becoming more aware of the fact that the individual and social factors may play a role.

The 'chicken-and-egg' issue remains an important one. There are still many questions to answer and variables to consider. 

Currently, hormone analysis is becoming more affordable and accessible. This allows psychologists to begin to tackle these critical questions. 

Military Muscle, a safe and natural testosterone booster that boosts your levels without side effects. 

Taking our powerful, unique fusion of natural ingredients can easily be incorporated into your daily routine. You will notice an increase in mood, energy and focus.

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