Brain-Sex Test

Jag hävdar att biologiska faktorer också spelar roll, och att det därför kan vara meningsfullt att tala om "manligt" och "kvinnligt" så länge det är underförstått att skillnaderna ibland är små och de individuella avvikelserna legio.

As testosterone affects the entire body (often by enlarging; males have bigger hearts, lungs, liver, etc.), the brain is also affected by this "sexual" differentiation;[13] the enzyme aromatase converts testosterone into estradiol that is responsible for masculinization of the brain in male mice. In humans, masculinization of the fetal brain appears, by observation of gender preference in patients with congenital diseases of androgen formation or androgen receptor function, to be associated with functional androgen receptors.[64]

There are some differences between a male and female brain (possibly the result of different testosterone levels), one of them being size: the male human brain is, on average, larger.[65] In a Danish study from 2003, men were found to have a total myelinated fiber length of 176,000 km at the age of 20, whereas in women the total length was 149,000 km (approx. 15% less).[66]

A study conducted in 1996 found no immediate short term effects on mood or behavior from the administration of supraphysiologic doses of testosterone for 10 weeks on 43 healthy men.[19] Another study found a correlation between testosterone and risk tolerance in career choice among women.[67][68]

The literature suggests that attention, memory, and spatial ability are key cognitive functions affected by testosterone in humans. Preliminary evidence suggests that low testosterone levels may be a risk factor for cognitive decline and possibly for dementia of the Alzheimer's type,[69][70][71][72] a key argument in life extension medicine for the use of testosterone in anti-aging therapies. Much of the literature, however, suggests a curvilinear or even quadratic relationship between spatial performance and circulating testosterone,[73] where both hypo- and hypersecretion (deficient- and excessive-secretion) of circulating androgens have negative effects on cognition.

The "evolutionary neuroandrogenic theory" focuses on the hormone testosterone as a factor influencing aggression and criminality and being evolutionarily beneficial during certain forms of competition. In most species, males are more aggressive than females. Castration of males usually has a pacifying effect on their aggressive behavior. In humans, males engage in crime and especially violent crime more than females. Their involvement in crime usually rises in the early teens to mid teens, at the same time as testosterone levels rise. Research on the relationship between testosterone and aggression is difficult, since the only reliable measurement of brain testosterone is by a lumbar puncture that is not done for research purposes. Studies therefore have often instead used more unreliable measurements from blood or saliva.[citation needed]

Most studies support a link between adult criminality and testosterone, although the relationship is modest if examined separately for each sex. Nearly all studies of juvenile delinquency and testosterone are not significant. Most studies have also found testosterone to be associated with behaviors or personality traits linked with criminality such as antisocial behavior and alcoholism. Many studies have also been done on the relationship between more general aggressive behavior/feelings and testosterone. About half the studies have found a relationship and about half no relationship.[74]

Testosterone is only one of a myriad of factors that influence aggression and the effects of previous experience and environmental stimuli have been found to correlate more strongly. A few studies indicate that the testosterone derivative estradiol (one form of estrogen) might play an even more important role in male aggression.[74][75][76][77]

Innan du slänger dig på tangentbordet, kan jag påpeka att dessa citat inte nämner någonting om spatiell förmåga, som tidigare nämnts. Vad de nämner är dock att könshormonet testosteron påverkar hjärnan och att dess koncentration verkar påverka bl.a. aggressivitet, vilket styrker mitt påstående om att biologiska orsaksförklaringar kan vara relevanta.

The "evolutionary neuroandrogenic theory" focuses on the hormone testosterone as a factor influencing aggression and criminality and being evolutionarily beneficial during certain forms of competition. In most species, males are more aggressive than females. Castration of males usually has a pacifying effect on their aggressive behavior. In humans, males engage in crime and especially violent crime more than females. Their involvement in crime usually rises in the early teens to mid teens, at the same time as testosterone levels rise.