Does intelligence differ according to gender?

Gender differences from a neuroscientific point of view


Another possibility for determining gender-specific differences is to specifically examine and compare only certain areas of the brain to which functions with gender-specific differences can be clearly assigned. For example, differences in the shape or size of certain nerve cells were found. A particularly spectacular attempt is the transplantation of "masculinity" onto a young female rat. Here, tissue from the brain area that controls sexual behavior is removed from newborn males and female siblings are implanted in place of the corresponding female brain area. These female rats then develop male copulatory behavior as adults. In mammals, the exchanged centers are in relatively small, inconspicuous areas of the diencephalon (in the hypothalamus) and in rats and other rodents show sex-specific differences in size. Similar centers are found in birds in the forebrain (prosencephalon). Here the differences between the sexes are even more pronounced, e.g. for the hyperstriatum ventral pars caudale, which controls the courtship song every year. Gorski (1984) also obtained unambiguous findings on the medial preoptic nucleus (medial preoptic area) of the rat. This nerve nucleus of the hypothalamus is four times larger in male rat brains than in female ones.
In the human brain, the evidence of morphological differences is not so clear-cut. This is not least due to the complex interaction of neural and hormonal components that influence behavior and cognitive abilities via the limbic system.

Neuropsychology and Lateralization

The cerebral cortex as a station for the conscious experience of sensory impressions proves to be relatively gender-neutral and bilaterally symmetrical in terms of shape. This morphological uniformity is offset by functional asymmetries of the hemispheres. Many researchers believe that language and spatial perception in particular are more lateralized in men than in women (asymmetry of the brain). The puberty marks an important point of development. Up to this point you can acquire languages ​​simply by being exposed to them, after which you have to actively learn them. Studies of the temporal course of lateralization, i.e. the specialization of the hemispheres of the brain (including left and right-handedness), in brain-damaged children showed that the ability to acquire language and lateralization are linked. If the children examined had suffered the damage before the end of the second year of life, they began to speak normally, regardless of which hemisphere was damaged. This plastic ability is gender-independent during early childhood development. In adults, pronounced gender differences occur after brain injuries. Speech disorders that affect the choice of words (aphasia) are most common in women when the front parts of the brain are injured, and in men when rear parts have been damaged. Difficulties in making adequate hand movements (apraxia) appear in women after lesions in the anterior left hemisphere and in men after lesions in the posterior regions. Men seem to be more inclined to specialize in their hemispheres than women. However, the investigation of left-handers again produced contradicting results. Left-handedness is attributed to the lower dominance of the left hemisphere. However, there are clearly more left-handed men than women. Even with right-handed men, women used the right hand more often than right-handed men. The gender differences in functional asymmetries thus vary from function to function: in some cases a stronger asymmetry can be observed in women, in others in men.
What significance does the different lateralization of men and women have for their intelligence quotient (IQ)? The Wechsler intelligence test for adults can be used for gender-neutral assessment. It consists of non-verbal and verbal sub-tests. As a measure of the IQ, both the IQ values ​​determined in the non-linguistic part and the IQ values ​​determined in the linguistic part are taken into account. In men, for example, damage to the left hemisphere affects the linguistic IQ more than the non-linguistic IQ.
In conclusion and in summary, it can be stated that women and men sometimes differ significantly in the individual cognitive abilities, but not in terms of overall intelligence, for which the IQ can, incidentally, only be one aspect of evaluation among many.

Lit .:Gorski, R.A.: Sex differences in the rodent brain: Their nature and origin. In: Sex differences in the brain. Eds .: De Vries, DeBruin, Uylings and Corner. Elsevier, Amsterdam-New York-Oxford 1984, pp.37-67. Kimura, D., Harshman, R.A..: Sex differences in brain organization for verbal and nonverbal function. In: Sex differeneces in the brain. Eds .: De Vries, DeBruin, Uylings and Corner. Elsevier, Amsterdam-New York-Oxford 1984, pp.423-439. Springer, S.P., German, G.: Left-right brain: functional asymmetries. Spectrum of Science, Heidelberg 1987.

Gender-typical differences in humans are well researched in the area of ​​sensory perception: women are more sensitive to touch and smells, notice changes in the arrangement of objects more quickly; Men see better in the middle field of vision, distinguish more details in moving objects, etc. There are also differences in more complex behaviors, even if some generalities are now in doubt. Boys do not necessarily appear to be aggressive more often than girls; the only aim is to vary the way in which aggressiveness is expressed. Boys prefer the more conspicuous, body-hugging variants, but an angry look, ridicule or verbal comments are also evidence of aggressiveness. The definition of the ranking within same-sex groups also differs accordingly. Already in early kindergarten age, as soon as children start to play in groups, the so-called Dominance hierarchy to find in girls the Validity hierarchy. These and other gender-typical behavioral dispositions are likely to be based on the division of labor family and group structure assumed early in human tribal history. It is assumed that the basic provision of supplies is ensured through the collecting activity of women, while animal food was obtained primarily through the hunting of male group members. However, this notion has been criticized more and more in recent years: it is increasingly assumed that women were also involved in the extraction of animal food. The gender-dependent, divergent orientation methods in the room - if orientation marks are removed, women have greater difficulty finding their way, men, on the other hand, if the spatial dimensions are changed - are tried to be explained by the division of labor in the nutrition sector. Survival and reproduction, the different participation in the care and the care tasks of the offspring therefore required different social strategies, characteristics and skills in the respective sex in the course of human history, which were reflected in these different behavioral dispositions. In the last few years, technically complex studies on the functioning of the brain have shown gender-dependent differences. For example, men prefer to use parts of the left brain hemisphere to decipher read words or spoken language, women use areas on both sides of the brain. The active areas of the brain also differ in mathematical tasks (the difference between the average mathematical performance of girls and boys has been decreasing more and more in recent years) and demands based on emotions (although morphological variations were also found). In some studies, however, it has also been shown that in some women the brain "functions" like in men. Differences in the tasks set usually become clearer when one asks very special skills. In the case of more complex tasks that require many skills to complete, the differences decrease, if they can be proven at all. The breakdown of gender-dependent properties with the help of new technologies in brain research is still at the beginning, and the number of test subjects examined is comparatively small due to the complex methods. Definitive statements about the causes are still not possible. The assumption is, however, that reasons are to be sought in the varying hormone balance (hormones) of the sexes in the course of development. Hormone changes constantly influence performance, thinking and feeling. Tests on women at different times of their menstrual cycle showed that during the high estrogen phase they did best on language tests, but their spatial skills deteriorated. The differences between the sexes are certainly also based on gender role-dependent socialization. The plasticity of the brain should not be neglected. Even short-term exercises change the way in which the brain organizes itself. The same can be expected for long-term socialization experiences. However, it is also assumed that, due to the early and spontaneous preference given to same-sex interaction and play partners for an individual, members of the same sex have more attractive behavior patterns, as they better correspond to their individual inclinations. The orientation of a child towards its own gender consequently additionally reinforces gender-typical behavior.