T is for testosterone in personali-T

One question I often get to answer on Quora is “Am I a T or an F type”. This is about the Myers-Briggs or Jungian distinction between Thinkers and Feelers. This is a personality trait that correlates roughly with trait Agreeableness in the Big 5 inventory, with high agreeableness associated with a softer or more female personality and low agreeableness associated with a tougher, more male personality. From an evolutionary point of view, these two personality profiles are most likely derived from a providing male profile (e.g. hunter) and a caregiving female profile. From a cognitive point of view, T brains are systemizing and F brains empathizing (cf. Simon Baron-Cohen).

I usually tell people to check their digit ratio, as it is indicative of prenatal exposure to high levels of testosterone (T) or estrogen (F), respectively. A low digit ratio (below zero, or ring finger longer than index finger) indicates high testosterone.

 

Low digit ratio male/T type (Source Wikimedia)

So, we arrive at the following correspondences:

MBTI	D2:D4 ratio	Big 5	hormone	Evolutionary function	Cognitive function
T	low	low agreeableness	testosterone	provisioning	systemizing
F	high	High agreeableness	estrogen	caregiving	empathizing

Of course, these correspondences are not set in stone and there may be considerable variation. Nor are testosterone and estrogen mutually exclusive or complementary. There are plenty of T men who are highly agreeable, for example. Nevertheless, this scheme may be a useful guideline. There are traits based on these types that can often already be observed in childhood.

T types display more

• Self-directedness and independence
• Interest in objects rather than people
• Anger
• Aggressiveness
• Competitiveness
• Leadership (sometimes dominance)
• Decisiveness
• Higher risk-taking

Cultures that have large differences in sexual dimorphism (among them also digit ratio), usually have more strongly defined gender roles too. A study has found that Hadza hunter-gatherer men do not have more masculine digit ratios than women. This finding ties in neatly with the high degree of egalitarianism between men and women in hunter-gatherers as compared to peoples with other modes of subsistence (farming and herding).

Women in politics are almost always T types, as you have to be tough to survive in politics: Angela Merkel, Hillary Clinton and Margaret Thatcher are only a few examples. Unfortunately, a lot of more traditionally-minded people are unwilling to vote for these women as they don’t always correspond to our stereotypes of what women should be like. I personally think that Hillary Clinton would have been a much more competent president than Donald Trump.

As people get older they often gravitate towards the middle, i.e. T types becoming more mellow and F types becoming a bit tougher. The birth of a child might also have effects on (both mothers' and fathers') hormone levels. These might be some of the reasons why people get different results when they take the Myers-Briggs personality test.