No, testosterone does not make you more successful

Oh, the testosterone. This so-called male hormone, because it has an average rate ten times higher in men, is plagued by stubborn myths. It would be partly responsible for the aggressiveness of the latter, their attraction to competition and power, and their socio-economic position. A recent study, published by a team from the University of Bristol, demonstrates that the link between socio-economic position and plasma testosterone levels cannot be explained by a causal effect of testosterone. In fact, all the statements we have just mentioned about testosterone are wrong and to understand this, you have to go back a little in the history of studies on this hormone.

studies among prisoners

The study of the links between testosterone and behavior, in particular aggressiveness, was carried out in the second half of the XX^and century mainly among prisoners. One of the first studies to test the hypothesis of a link between plasma testosterone levels and aggression was published in 1972. Subsequently, other studies will follow, giving very scattered results in terms of matter of correlation. A 1995 study will attempt to address the issue with a decent sample to achieve sufficiently robust statistical power and conclude that there is a link between plasma testosterone levels and deviant and aggressive behavior in prisoners.

Curiously, this study does not mention considerable limitations in its discussion such as the social environment and the very particular population that the prison environment constitutes, reverse causality biases and various confounding factors, for example the time of day at which samples are taken. The authors, Georgian scientists, are probably influenced by civil war which has just ended in their country and the potential enthusiasm aroused by the project of the genome human to explain the behavior of individuals by biology alone.

Indeed, the search for a strict biological determinism in terms of deviant behavior is reassuring: if an individual X is predisposed to commit crimes, this means that crimes can easily be prevented on the one hand and on the other , essentializing the distinction between good and bad citizens, which reinforces the status quo in terms of the social model. That era is over. We now know that it is the social, political and economic environment as well as the individual history of people that mainly determine their complex actions. Biology plays a marginal role in this respect in human beings. Even for choices a priori more primitive, such as the preference for sugar partly biologically determinedone could argue that the context (preconceived ideas about weight, cult of thinness, etc.) predominates in humans when we see how big the market for sweetened beverages is still growing. But back to our hormones: Misconceptions about testosterone persist while the empirical evidence supporting them fails to support them.

Hormones have no specific effect on behaviors

Oxytocin would be the hormone of attachment, testosterone that of aggression and the conquest of power, while dopamine would be the neurotransmitter from happiness. In their concern for excessive simplification, some media convey these associations by linking a hormone to well-defined social behaviors. The scientific literature on the subject is much more cautious. Indeed, most literature reviews, whether about oxytocin or testosterone, rather suggest eminently contextual roles of these hormones. Therefore, depending on the context and other individual variables, oxytocin is associated in some experiments with distrustat ethnocentrism or jubilation in the misfortune of others if it is beneficial to us.

About the literature regarding testosterone, she suggests that this hormone is also associated, depending on the context, with altruistic actions and prosocial behaviors. By way of example, one could mention this 2011 study which shows that in a group of women, the sublingual administration of a single dose of testosterone causes a substantial increase in fair negotiation behavior, thereby reducing conflict and increasing the effectiveness of social interactions. However, a very interesting point should be noted in this study: women aware of having received testosterone (as opposed to those who received testosterone blindly) show more aggressive behavior. A fact that suggests that the ideas we have about a hormone can also influence our behavior. In conclusion, we know that the link between testosterone and aggression is generally non-existent in large samples. Nevertheless, testosterone is constantly associated with behaviors that allow obtaining or maintaining a certain social status. Then how the original Bristol University study that we have mentioned suggests that this link is not causal?

Genes predisposing to high plasma testosterone do not correlate with socioeconomic status

This is using data from the British BioBank and of Mendelian randomization that Dr. Amanda Hughes’ team came to this conclusion. Scientists have identified the variants genetic predisposing to high plasma testosterone levels. Unlike plasma testosterone, the presence of genetic variants is neither sensitive to the time of day, nor to the social environment to which we belong, nor to what we have just eaten or to our level of activity. physical. This guards against reverse causality bias, that is to say, detecting an association and thinking that A causes B while it is B which causes A. Here, this would amount to saying that the plasma testosterone level predisposes to a higher socioeconomic level while it is the higher socioeconomic level that actually results in a higher plasma testosterone level.

While the investigators have confirmed the links between plasma testosterone level, socioeconomic position and state of health, the correlations disappear or become excessively less robust when the plasma testosterone variable is replaced by genetic variants predisposing to a high level of testosterone. . Based on this observation, the authors suggest that the associations reported so far between plasma testosterone, socio-economic position and health are probably due to confounding factors or reverse causality.