Rumors about testosterone
Excerpt from the book of neuroscientist Robert Sapolsky "Biology of Good and Evil" about how testosterone is associated with aggression
Together with Alpina Non-fiction Publishing House we publish an excerpt from the book of neuroscientist Robert Sapolsky "Biology of Good and Evil" about the nature of good and bad actions and the factors influencing our behavior. Translated from English by Julia Abolina and Elena Naimark.
In males, including men, testosterone is released by the testes as a result of a cascade of influences along the hypothalamus – pituitary – testicles axis, and the testes are the last link of this descending cascade. At the same time, testosterone affects the cells of the whole body (including, of course, neurons). And as soon as it comes to aggression, testosterone becomes the main accused hormone.
Comparisons and reasons
Why is it believed that males, and in particular men (and in all cultures), are responsible for aggression and violence? So what about testosterone and related hormones? (All these hormones are called by the general word "androgens", and for simplicity I will use this term as a synonym for testosterone, unless I need to clarify something specifically.) Males of almost all types have more testosterone than females (here a certain amount of androgens is secreted by the adrenal glands). In addition, aggression in males is more pronounced with high testosterone levels (for example, in adolescence or in species with seasonal cycles during mating).
So testosterone and aggression are related. Note further that there are especially a lot of testosterone receptors in the amygdala; there are also a lot of them at the "transshipment station" (in the core of the terminal strip bed), through which the amygdala is connected to other parts of the brain, and in the main areas in its zone of influence (hypothalamus, central gray matter, frontal cortex). But these are nothing more than comparisons. To prove that testosterone is the cause of aggression, experiments on the type of "removal" and "substitution" will be needed.
"Removal" is a variant of male castration. Does the level of aggression decrease at the same time? Yes, it is decreasing (and in humans too). This suggests that something coming from the testes causes aggression. Is this something testosterone? We will perform a replacement – we will add the missing hormone to the castrate. Will the aggression reach the pre-castration level? Yes, it will (and people too). Conclusion – testosterone is the cause of aggression. And now let's see to what extent this is incorrect.
Difficulties begin as soon as we undertake to measure the level of aggression immediately after castration: the average indicators for all species collapse, but – and this is significant – not to zero. Maybe we castrated carelessly and did not completely remove the testes? Or is some small amount of androgens secreted by the adrenal glands to maintain aggression? But no, even when testosterone and all androgens are completely eliminated, aggressive behavior in one form or another still remains. This means that some part of the aggression in males does not depend on testosterone.
This conclusion is reliably confirmed by monitoring of men who are sentenced to castration for sexual crimes, as is customary in some American states. As a legal punishment for sexual crimes, they use "chemical castration": convicts are forcibly given drugs that either suppress the release of testosterone or block testosterone receptors.
As a result, castration reduces the level of sexual tension in criminals with strong, uncontrollable, pathological sexual urges. But at the same time, their relapse rate does not decrease. As stated in one study based on the analysis of a wide array of data, "if a sexually motivated crime is motivated by a demonstration of rage or power, then it is useless to give [antiandrogen] drugs to such malicious rapists."
These observations lead to an extremely important conclusion: if the male often expressed aggression before castration, he will continue in the same spirit after it. In other words, such a male does not need testosterone too much to maintain aggression, it is a consequence of social learning.
Let's move on to the next point that calls into question the primacy of testosterone. How does the individual level of this hormone correlate with aggression? If one person has an average testosterone level higher than another, or this week he has it higher than last week, does this mean that this individual is more aggressive? It would seem that all these questions should be answered in the affirmative, because studies show a correlation between individual testosterone levels and higher rates of aggression. But aggression itself stimulates the release of this androgen; so it is not surprising that testosterone is also increased in more aggressive individuals. The eternal problem of chicken and eggs cannot be solved in this way.
Let's put the question better this way: is it possible to predict aggression based on individual differences in testosterone levels? It turns out that for birds, fish, mammals and – this is especially important – primates, the answer is generally negative: no, we can't. A great many similar studies were also conducted for humans, while a variety of aggression indicators were taken into account. The answer was clear in all cases. Here is a quote from the final review of 2006 by British endocrinologist John Archer: "The relationship between testosterone levels and aggression in adults [people] is very weak and unstable, and ... in volunteers, when taking testosterone, it does not increase." The brain does not notice changes in testosterone levels if fluctuations occur within the normal range. Another thing is if the amount of hormone is increased above the physiological norm and it becomes more than the level that is characteristic of the normal work of the body. Here we find ourselves in the world of athletes and bodybuilders abusing testosterone-like anabolic steroids; in this case, the risk of aggression really increases. However, there are two "buts" here: an ordinary person will not take such drugs, and those people who choose this path are already predisposed to aggressive behavior; they have additional androgen intake that causes anxiety and paranoia, and aggression may be a side result of these syndromes.
Thus, aggression speaks more about social learning than about testosterone. Different levels of this hormone do not explain why some are more aggressive than others. How does testosterone affect behavior anyway?
The effect of testosterone in detail
When we see a very pronounced emotion on someone's face, we copy this expression ourselves a little; testosterone also reduces the ability to such "empathic" copying. In addition, this androgen worsens the quality of emotion recognition by the eyes, because of it, unfamiliar faces - unlike familiar ones – cause stronger activation of the amygdala and are perceived more cautiously.
Testosterone strengthens self-confidence and increases optimism, moderates fear and anxiety. This explains the winner effect in laboratory animals: winning a fight increases the appetite for other similar skirmishes and, accordingly, the number of subsequent victories. In part, this success indicates that winning stimulates the production of a hormone, which, in turn, increases the supply of glucose to the animal's muscle tissues and accelerates metabolism, and because of this, the winner's pheromones smell more "menacing".
In addition, the gain increases the number of testosterone receptors in the nucleus of the bed of the terminal strip (the "intermediate station" through which the amygdala communicates with the rest of the brain). And this, as we know, increases sensitivity to this hormone. Any success – in sports, chess or business – will raise testosterone levels.
Well, confidence and optimism are fine. It is to them that endless rows of self-development books call us. But the insidious hormone makes us too arrogant, too optimistic, which can have bad consequences. In one experiment, participants in pairs were asked to consult with each other before making a decision. Under the influence of testosterone, the subjects considered their own decision correct and did not pay attention to the judgment of their partners. This androgen turns people into boors, egoists and narcissists.
Testosterone adds impulsiveness to people, makes them take risks, make the stupidest decisions in simple situations. And it turns out this way because it reduces the activity of the prefrontal cortex and worsens its functional connection with the amygdala, while activating the interaction of the latter with the thalamus - and this, as we already know, is a short path of sensory information to the amygdala. Thus, the decisive vote is given to instant inaccurate impulses, and rational "stop-and-think" signals from the frontal cortex play a subordinate role.
A person experiencing fearlessness, self-confidence and boundless optimism feels great. Therefore, it is not surprising that testosterone is perceived favorably. Rats will try their best (push the lever) to get a portion of testosterone; they demonstrate a "conditioned reflex choice of location", i.e. they return to the corner of the cell where they were injected with androgen. It's like they're talking: "I don't know why, but I feel so great when I stand in that corner."
The neurobiological basis exactly matches these observations. In order to develop a conditioned reflex of "place", dopamine is needed, and testosterone just increases the activity of the ventral tire area, from where mesolimbic and mesocortical dopamine axons originate. In addition, the conditioned reflex of "place" is produced if testosterone is delivered directly to the nucleus accumbens – that is, where most projections come from the ventral tire. When a rat wins a fight, the number of testosterone receptors increases in the ventral tire and the nucleus accumbens, as a result of which sensitivity to the hormone and to "testosterone joy" increases.
So, there are a lot of subtle moments in the effect of this androgen on our behavior. But at the same time, we are not able to draw any hard conclusions, because any of our observations can be interpreted either way. Testosterone increases anxiety – you feel fear and, reacting to it, become aggressive. Testosterone reduces anxiety – and you become arrogant, arrogant and, accordingly, aggressive in advance. Testosterone increases the desire to take a chance: "Hey, I'll rely on luck and defeat my neighbor!" Or so: "Hey, I'll rely on luck and negotiate with him in peace!" Because of testosterone, you get better: "I just won with such style, but let's fight again." Or like this: "Let's all make up and shake hands."
So the result of the effect of this hormone depends to a great extent on the situation – this is the most important conclusion.
The conjugate effect of testosterone
Depending on the situation, context means that testosterone is not the cause of the act X, but rather enhances the effectiveness of something else, which is the cause of X.
To illustrate this statement, we present a classic 1977 study of male dwarf monkeys talapoin. Males who were somewhere in the middle of the hierarchical ladder of the group (say, at step 3 out of 5) were injected with testosterone, increasing the level of aggression. And what is it? Our "natestosterone" friends rushed to attack the male leaders of stages 1 and 2? Not at all. Instead, they became nightmarish boors in relation to the unfortunate relatives of steps 4 and 5. The hormone did not lead to the emergence of new aggressively loaded social ties, it only strengthened existing ones.
Studies have shown that in humans, testosterone does not increase the basic activity of the amygdala; it heats up its reaction and increases cardiac activity at the sight of threatening faces (but not neutral or joyful). Similarly, testosterone did not make the subjects more selfish in the situation of economic games; but they became more vindictive in response to injustice, they increased, so to speak, revanchist reactive aggression.
Dependence on context is also manifested at the level of neurobiology. This hormone shortens the refractory period (the period of non-excitability) of neurons in the amygdala, as well as in the hypothalamus, where the processes come from it. Let's take into account that the refractory period occurs in the neuron after the action potential. At this moment, the potential of the neuron is characterized by hyperpolarization (i.e., the neuron carries a greater negative charge than usual), leading to the fact that it is less excitable; as a result, a period of rest follows after the action potential. Therefore, a shorter refractory period means an increased frequency of action potentials.
Let's ask ourselves: what increases the frequency of action potentials – testosterone? No. Testosterone causes neurons to be excited more often if some other stimulus acts on them. This is how our hormone enhances the amygdala's response to scary faces, but not to any others. So, here's what we have: if the amygdala already reacts to a certain social stimulus, then testosterone increases the strength of the reaction.
The key generalization: the hypothesis of "challenge" Yes, testosterone will aggravate the existing propensity for aggression, but it will not create it out of nothing, i.e. its effect is conjugate and reinforcing. With an eye to this rule, an inspiring hypothesis of "challenge" was proposed, within the framework of which all available information about the action of androgen fits perfectly. John Wingfield, a brilliant endocrinologist and behaviorist, and his colleagues from the University of California at Davis expressed an interesting idea in 1990. Their idea was that an increase in testosterone levels increases aggression only in a "challenge" situation. That's exactly what happens.
This hypothesis explains why the baseline testosterone level does not affect the subsequent manifestation of aggression, and also why an increase in the amount of the hormone during puberty, sexual stimulation and at the beginning of the mating season also does not cause its growth.
But when fate challenges, everything changes. In many primates, testosterone levels rise at those moments when a new dominance hierarchy is established in the group or the old one is rebuilt. In humans, its number increases, for example, during sports competitions, both in team and individual sports – basketball, tennis, rugby, judo and wrestling. The same is observed before the competitions, and (to an even greater extent) after them, especially among the winners. It is significant that testosterone levels also rise among fans when they witness the victory of their favorite team; this means that not muscle activity, but rather the psychology of dominance, social identification and self-esteem is linked to an increase in the amount of this androgen.
The most important thing here is that an increase in testosterone levels after a test makes aggressive behavior more likely. Think about it: the amount of testosterone increased, and it got into the brain. If this happened in a conflict situation, you will direct close attention towards the source of aggression. If testosterone has risen due to the fact that the days have become longer and the mating season is approaching, someone goes a thousand miles to look for a mate. If the amount of hormone has soared because the age has come, you will start giggling stupidly in the presence of a clarinetist girl from a music class. The dependence on context is amazing!
The "challenge" hypothesis has a second part. The rise in testosterone levels after the test does not provoke aggression. Instead, it leads to the behavior that is necessary to maintain social status. And that changes everything.
Well, maybe not quite everything: after all, in male primates, maintaining status requires aggressive behavior or at least the threat of aggression - from a brutal attack on an opponent to an intimidating "you–can't-even-imagine-who-you-messed with" look.
And now let's talk about the stunning discovery. What happens if maintaining the status requires being... good? This is exactly the question that researchers Christoph Eisenegger and the already mentioned Ernst Fehr from the University of Zurich asked themselves. The participants of the experiment played the game "Ultimatum", where they had to decide how much money to keep for themselves and how much to offer to the opposing player. The opponent could accept or reject such a decision, and if he did not accept the proposed division, then none of the players received anything. Previous studies have shown that the first player, in case of rejection of his offer, feels insulted, pushed into the background, especially if the rejected offer becomes known in the following rounds. In other words, in this scenario, status and reputation are based on honesty and fairness.
What happens if the subjects are given testosterone preparations beforehand? Participants become more generous. The hormone will force you to do exactly what in this social context will be considered sexually attractive. And this requires a rather intricate system of neural-endocrine connections, subtly reacting to social learning. It is truly difficult to find another similar study that will so reliably deprive testosterone of an "aggressive" reputation! There was another curious aspect in this study that pushed the myth of testosterone even further away from the real state of things.
As in all such blind experiments, the participants did not know what they were being given – in this case it was either saline or testosterone. Those who thought they had received testosterone (regardless of what they were actually injected with) made less generous offers in the game. In other words, you become shameless not from the hormone itself, but from the belief that the cause of rudeness is a sea of testosterone.
Additional research has shown that in the right situation, this androgen promotes prosocial behavior. In one of the staged cases, when self-pride was supposed to be based on honesty, testosterone reduced the number of episodes of cheating in the game.
In another case, where the players had to keep some money for themselves and put some into the "common pot", testosterone also forced the majority to pro-social decisions.
What does all this mean? And the fact that thanks to testosterone, we strive harder in all acceptable ways to obtain and maintain social status. And the key in this phrase is the phrase "acceptable ways".
Create the right social conditions and with an increase in hormone levels, people will rush, overtaking each other, to do good deeds. In our world, where men's aggression is found at every turn, the problem is not that testosterone increases aggressiveness. The problem is how often we encourage this aggression.
About the author:
Robert M. Sapolsky – professor of Neurology and Neurosurgery at Stanford University.
Portal "Eternal youth" http://vechnayamolodost.ru