> You can not measure the testosterone in a group and make a prediction about who is going to commit a crime.
Well, if the group is mixed, with both men and women, then you can predict that 95% of the violent crimes will be committed by people with higher testosterone (i.e. men). Surely in that sense it's about testosterone, not genitalia?.
That's why it's very surprising to hear that the _level_ of testosterone among men has no predictive power.
Nope, higher testosterone is not an predicting factor for violent crimes. If you measure a mixed group what you get is the same correlation as you would get with any other sex trait.
Many research papers has been written on the topic of testosterone and violence, including meta studies. The general conclusions is... there is a weak link between testosterone and violence. No cause and effect, but there is a small amplification of existing behavior, a common finding among endogenous studies.
The full reason is complex, but a simplification is that testosterone increase preexisting behavior in relation to social status hierarchy. It makes individuals spend more energy in defending their place on the ladder (spending more time looking at faces to recognize threat, increased response to threatening faces, more suspicion against ambiguous faces). This in turn has a link towards violence, but only in cultures where status is given as an reward for violence.
But there is an additional complexity that should be mentioned. A lot of the effects of hormones such as testosterone only happen as a result of changing levels of hormones rather than absolute values. The absolute value has less of a predictive effect then changes over a short time frame.
Interesting. So, my understanding is that most male violence is committed by males between the ages of 15 and 25 (roughly). That is also generally the period of highest testosterone levels in men. What would cause the spike in violence if not the elevated testosterone levels?
I have a couple guesses:
1. This may be a period in which men experience the greatest status uncertainty and so may resort to violence in an attempt to solidify their place in a social hierarchy.
2. This is generally the age range during which many disorders that are more prevalent or severe in men (such as schizophrenia, bi-polar, etc.) begin to manifest.
15 to roughly 25 is the period when the frontal cortex is maturing, and also the period where peer influence has the most impact on development. The frontal cortex is highly involved in silencing the fear response, and in determining the socially correct response to threats, particularly threats towards a person's social position (a common theme for studies around violence).
1) I have not read any study however that looked at periods of social uncertainty, but it sounds plausible.
2) My guess would go towards the relation of frontal cortex maturation. Before fully maturation, other parts of the brain "step in" and handle some of the frontal cortex' role, but by around age 25 they stop doing that.
> My guess would go towards the relation of frontal cortex maturation. Before fully maturation, other parts of the brain "step in" and handle some of the frontal cortex' role, but by around age 25 they stop doing that.
So, do you mean that such disorders originate from the frontal cortex, and that the reason they manifest by 25 or so is because it is at that point that the frontal cortex is no longer "supported" by other parts of the brain and it's flaws become apparent? Interesting if so.
Of course it’s an excellent predictor in a MIXED group. Testosterone predicts BEING male or not and being male predicts violent crime, almost perfectly.
Well, if the group is mixed, with both men and women, then you can predict that 95% of the violent crimes will be committed by people with higher testosterone (i.e. men). Surely in that sense it's about testosterone, not genitalia?.
That's why it's very surprising to hear that the _level_ of testosterone among men has no predictive power.