MadSci Network: Neuroscience |
Although I am not an expert in the field of human neuropsychology, from what I've read so far no such correlation seems to exist. Sounds like one of these popular distortions of scientic findings (a.k.a. modern myths) to me. First of all, in normal human beings the brain hemispheres usually do not function in isolation from one another; usually they cooperate on most tasks. One hemisphere might be dominant but the other usually has at least a rudimentary capability, i.e. contributes a little bit. In addition, if anything at all, then it is your hormones and their (possible) influence on brain development, that make you masculine or feminine. This should affect the entire brain (including subcortical, i.e. more primitive areas, which contribute a lot to human behavior as well) and not a single hemisphere. What you might be referring to is a hypothesis that's been around for some time. Testosterone, the male sex hormone, is believed to slow down development of the left hemisphere and thus account for the different brain organizations of males and females. This hasn't conclusively been proven or validated though. I suggest reading chapter 10 from the Kolb and Whishaw book (1996) and chapter 1 (pp. 43 to 56) from Tavris (1992) if you're interested in more details. Note that during the last 30 to 40 years differences (e.g. in the scores on collegiate admission tests) have vanished almost entirely. Men and women have virtually equivalent verbal and reasoning skills and the scores on mathematical ability tests differ only slightly. (Which might incite suspicion that earlier tests were either biased or that in our modern day society some differences level out due to environmental factors, e.g. co-ed education, exposure to technology in every-day life, etc.) There is a noteworthy exception after all: men/boys by far outnumber women when it comes to exceptional mathematical giftedness. The reason for this has not yet been found. In addition, it does not give us a clue as to whether these persons will also succeed in life or in their jobs (or if they are likeable or not). One must consider that functional or physiological differences (brain organization, cerebral blood flow, brain activation patterns, etc.) do not necessarily show up as behavioral differences. The output may be equivalent or the same even though the inner workings vary! Scientific investigation into verbal and spatial abilities has produced incoherent/controversial results. Some researchers find more or less significant differences and others don’t. E.g. check this reference or this one. Here’s another selected one. Are these diverging outcomes a result of methodological differences (e.g. the kind of test used, sample bias, or the like)? Or do researchers interpret their results in a different way based on their personal assumptions/theories? After reading Carol Tavris's book 'The mismeasure of woman' I suspect that a great many of the gender differences one notices are probably not based on biology but rather on sociocultural factors such as education, (identification with) gender role , socialization, and opportunities, in general subsumed under the term of 'life history'. For example, one possible explanation for differences in scientific knowledge between men and women might be the degree of exposure to science and technology during childhood and early adulthood (teen-age and thereafter). So the question remains: what makes us clever in general? Nature or nurture or an interplay of both? To give you a tentative answer: Even if the sexes differ in their abilities they (and accordingly every individual as well) have to be treated in their own right. Trying to root up ‘significant differences’ based on biology can sometimes leave the impression of claiming a naturally justified superiority of one sex over the other. Sadly enough, such alleged scientific findings and popular beliefs have been abused to subdue/suppress women in the past. In case you have any other questions, feel free to get back to me. References: 1. Crucian GP, Berenbaum SA (1998): Sex differences in right hemisphere tasks. Brain Cogn 36(3):377-89 2. Halpern DF, Haviland MG, Killian CD (1998): Handedness and sex differences in intelligence: evidence from the medical college admission test. Brain Cogn 38(1): 87-101 3. Jaeger JJ, Lockwood AH, Van Valin RD Jr, Kemmerer DL, Murphy BW, Wack DS (1998): Sex differences in brain regions activated by grammatical and reading tasks. Neuroreport 9(12):2803-7. 4. Kerns KA, Berenbaum SA (1991: Sex differences in spatial ability in children. Behav Genet 21(4):383-96 5. Kolb B and Whishaw IQ (1996): Fundamentals of Human Neuropsychology. WH Freeman and Company. 6. Kramer JH, Delis DC, Kaplan E, O'Donnell L, Prifitera A (1997): Developmental sex differences in verbal learning. Neuropsychology 11(4):577-84 7. Lynn R (1998): Sex differences in intelligence: a rejoinder to Mackintosh. J Biosoc Sci 1998 Oct;30(4):529-32; discussion 533-9 8. Nagae S (1985): Handedness and sex differences in the processing manner of verbal and spatial information. Am J Psychol 98(3):409-20 9. Stumpf H, Klieme E (1989): Sex-related differences in spatial ability: more evidence for convergence. Percept Mot Skills 69(3 Pt 1):915-21 10. Tavris C (1992): The mismeasure of woman. Simon and Schuster 11. Wisniewski AB (1998): Sexually-dimorphic patterns of cortical asymmetry, and the role for sex steroid hormones in determining cortical patterns of lateralization. Psychoneuroendocrinology 23(5):519-47
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