Hormonal determinants of personality − Rakyat Biologi

The brilliant endocrinologist named Helmuth Nyborg has proposed a theory which he calls the covariance-androgen/estrogen (GTC-A/E) model. This model claims that the balance of androgen and estrogen concentration levels is the critical variable in determining not only “ average ” behavioral sex differences, but also important individual differences in behavior and even in personality traits in the general population. So in fact, it is a biological (hormonal) theory of androgyny, the relative “maleness” or “femaleness” of a person. That's why this approach is also known as “hormotyping”. Everybody knows that there is some overlap in the sexes with regard to sex-typical personality traits: there are some very aggressive women and there are some very very fearful men. What many people do not know is that there is also some overlap of sex-specific hormone levels. Some women have hormone levels that resemble the male profile, and some men have a female-like hormone profile. Nyborg’s model predicts that people who have low levels of their own sex hormone and high levels of the opposite sex’s hormones will be psychologically androgynous. In other words, these people are predicted to obtain an immediate score on any measure of any behavioral, attitudinal, mental or ability trait that is sex-specific. The model even makes a fascinating and very risky prediction about distributions of mental abilities as a function of race. Black males have highest testosterone levels, Caucasians being intermediate and Asians lowest. This leads Nyborg to predict a fetal testosterone overshoot in blacks -leading to depressed brain estradiol, leading to relatively weak visuospatial ability. Asians are predicted to have the highest relative visuospatial ability level. The model also predicts greatest physiognomic sexual differentiation in blacks and the least in Asians. Note that the model is not making a prediction about any race difference in overall mental ability. Does the model work ? Because hormone levels are technically so difficult and expensive to measure, the chickens have not yet come home to roost as far as the GTC-A/E model is concerned. Most of the scientific work done so far on the theme of androgyny has eschewed the measurement of sex hormones.

A researcher named Sandra Bem has developed a well validated psychological test of androgyny (the BEM sex-role inventory) that has been used in many research projects. Bem has developed a theoretical model of psychological masculinity and femininity which distinguishes itself from Nyborg’s. She believes that masculine and feminine traits do not necessarily segregate in blocks. More specifically, she has found that people are not necessarily more or less feminine or more or less masculine. They can also be very highly masculine on some traits and very highly feminine on other traits. They can also be very low on both, a condition which is termed «undifferentiated». This model is called the «orthogonal or independent» model. Reinisch and her colleagues have adopted an intermediate theoretical position termed the «oblique» model. It postulates that the independence of masculine and feminine traits is a matter of degree.

It is very very difficult to do research on effects of prenatal events on pre or postpubertal activities and behaviors in humans. It would be extremely convenient if we could find reliable markers of degree of prenatal masculinization or feminization. The German physician W.S. Schlegel has tried to develop such a marker. The shape of the hips is a very strongly sexually dimorphic trait, which could tightly depend on prenatal hormonal events. Nevertheless hip shape varies enough within each sex to allow for estimation of «degree» of prenatal masculinization or feminization. At any rate, sex-specific personality traits have repeatedly been found to correlate with hip shape, suggesting hormonal effects on human psychology that could in fact answer to simpler psychoendocrinological models than those of Nyborg, Bem or Reinish.

Nevertheless, there is unquestionably a great deal of wisdom in the idea of «independence» of male and female traits. Prenatal hormonal manipulation of mammals has resulted in all kinds of realignments of sex-specific traits which can in no way be reduced to simple feminization versus simple masculinization. Also, in higher primates, especially humans, who rely the most on learning and who’s behavioral repertoires are the most plastic (adaptible), it seems to me that the best adapted male or female will be the one who can express male-like or female-like behavior according to the demands of the varying situations he or she finds himself or herself in.