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PINK BRAIN, BLUE BRAIN: Females and Males in Math and Science

PINK BRAIN, BLUE BRAIN: Females and Males in Math and Science. Lise Eliot, PhD Dept. Neuroscience Rosalind Franklin University of Medicine & Science The Chicago Medical School. Synopsis.

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PINK BRAIN, BLUE BRAIN: Females and Males in Math and Science

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  1. PINK BRAIN,BLUE BRAIN:Females and Males in Math and Science Lise Eliot, PhD Dept. Neuroscience Rosalind Franklin University of Medicine & Science The Chicago Medical School

  2. Synopsis • Sex differences are real, but generally smaller than current Mars/Venus beliefs. • Boys and girls have different interests, but do not “learn differently.” Existing research has identified few boy-girl brain differences, while such differences in adults are shaped in large measure by neural plasticity. • Girls’ steady recent advances in math, science and athletics prove abilities are malleable, but we have further to go. • Earlier spatial skill training may help girls transition from high school to college math and science. • The biggest hurdle for getting more women into STEM careers remains cultural.

  3. Study of Mathematically Precocious Youth (SMPY), Benbow et al. Ratio of boys:girls above 700 Sources: Association of Women Mathematicians (2006); R. Monastersky, "Primed for Numbers?" Chronicle of Higher Education, 51, no. 26 (2005): A1.

  4. U.S. college enrollment gap Percent of undergraduate enrollment Source: National Center for Educational Statistics

  5. College enrollment, raw #s Source: National Center for Educational Statistics

  6. STEM crisis? % of doctorates awarded to women National Center for Educational Statistics (2004) Trends in Educational Equity of Girls & Women

  7. NAEP math data

  8. Math SAT gap

  9. PISA international math

  10. PISA: international reading assessment

  11. Plasticity in visual development Normal rearing strabismus One eye shut D. Hubel, T. Wiesel

  12. frontal lobe visual cortex Cortical synaptic pruning # synapses 0 4 8 12 16 20 40 60 80 age in years

  13. Activity-dependent myelination (RD Fields (2005) Neuroscientist, 11:528-31) • A new concept: plasticity was thought to be limited to gray matter. • Repeated activity (e.g., piano practice) increases thickness of the corpus callosum.

  14. Psychological differences ♂>♀ ♀> ♂ • Spatial ability • Math & science tests • Mechanical reasoning • Activity level • Gross motor • Physical aggression • Competition & risk-taking • Throwing & targeting • Verbal fluency • Reading, writing, spelling • Most perception • Associative memory • Fine motor • Relational aggression • Fear & conscientiousness • Social perception

  15. Quantifying effect sizes M(males) – M(females) Standard Deviation d = • Positive d means males score higher. • Cohen’s convention: d < 0.2 is a small effect d ~ 0.5 is a medium effect d > 0.8 is a large effect

  16. Extensive meta-analyses of traits ranging from cognitive ability to moral reasoning reveal most differences are small, by Cohen’s criterion, and grow with age. • Concludes her discussion by citing the “costs of inflated claims of gender differences.”

  17. Size matters d = 0.35 d = 2.6 "Women are from North Dakota. Men are from South Dakota” # of cases # of cases Science achievement test Height

  18. “Small differences grow into troublesome gaps”

  19. Proportion of total looking time Connellan, Baron-Cohen et al. (2000) Study of 100 newborns, widely cited in recent media and books as evidence for innate sex difference in preference for “people versus objects.” Caveats: JC’s live face; not “blind” to sex of newborns; many other studies find no sex difference in face or object perception (Elizabeth Spelke, American Psychologist, 2005).

  20. Woodward Elementary, Volusia County, Florida

  21. Fenson et al. (1994)Monograph. Soc. Res. Child Dev. Language learning in toddlers • Similar findings in China and Sweden, where d= 0.2. • In behavioral genetic studies, sex accounts for just a small proportion (<3%) of the total variance in children’s language skill. • e.g. Kovas et al., Child Development, 76:632-51, 2005.

  22. Reading “Report Card” (US)

  23. Sex difference in aggression

  24. Toy preference (Servin et al. 1999) Amount of time spent playing with boys girls

  25. Mental rotation in infantsMoore & Johnson (2008); also Quinn & Liben (2008) • Largest cognitive difference between men & women (d=0.56). • However, the difference grows through childhood and adolescence, and experiences like sports and video games have been shown to improve performance in both sexes.

  26. Water-level test (Piaget)

  27. Line orientation Which numbered line matches the angle of each of these? 7 8 6 9 5 10 4 3 11 2 12 1 13

  28. Role of hormones estrogen testosterone Fetus Newborn Infant Child Adolescent Adult

  29. Sex hormones & behavior • Organization (fetal development) • Prenatal testosterone (T) masculinizes animal behavior. • In humans, prenatal T clearly influences sexual orientation and play behavior, but little effect on gender identity or cognition. • Activation(puberty onward) • Testosterone is associated with aggression, competition and sex drive (in both sexes), but only weakly to cognitive skills. • Equivocal findings for cognitive effects over menstrual cycle or following hormone supplementation in teens, transsexuals, and post-menopausal women.

  30. Hierarchy of prenatal androgen effects in CAH Activities & interests activity level & inhibitory control Sexual orientation Prenatal androgens Personality Cognitive abilities After Sheri Berenbaum (2005) “Prenatal androgens and the ontogeny of behavior” Gender identity

  31. LouannBrizendine, Inc. “Anyone who has raised boys and girls or watched them grow up can see that they develop differently, especially that baby girls will connect emotionally in ways that baby boys don’t.” “Psychoneuroindoctrinology” -Nature book review “In all menstruating women, the female brain changes a little every day. Some parts of the brain change up to 25 percent every month.” Girls, not boys, come out wired for mutual gazing. Girls do not experience the testosterone surge that shrinks the centers for communication, observation, and processing of emotion… “Boys from the get-go learn differently than girls do”

  32. What are teachers reading? “Girls and boys play differently. They learn differently. They fight differently. They see the world differently. They hear differently…Girls and boys behave differently because their brains are wired differently.” “Millions of years of human history are inherited in the neural systems of male and female children…and the difference has profound effects on how boys and girls act, live, and learn.”

  33. Class groupings by hormones? Three years ago, Jeff Gray, the principal at Foust Elementary School in Owensboro, Ky., realized that his school needed help—and fast. Test scores at Foust were the worst in the county and the students, particularly the boys, were falling far behind. So Gray took a controversial course for educators on brain development, then revamped the first- and second-grade curriculum. The biggest change: he divided the classes by gender. Because males have less serotonin in their brains, which Gray was taught may cause them to fidget more, desks were removed from the boys' classrooms and they got short exercise periods throughout the day. Because females have more oxytocin, a hormone linked to bonding, girls were given a carpeted area where they sit and discuss their feelings. Because boys have higher levels of testosterone and are theoretically more competitive, they were given timed, multiple-choice tests. The girls were given multiple-choice tests, too, but got more time to complete them. Gray says the gender-based curriculum gave the school "the edge we needed." Tests scores are up. Discipline problems are down. This year the fifth and sixth grades at Foust are adopting the new curriculum, too. -Peg Tyre, Newsweek, Sept. 19, 2005

  34. Flechaire et al. Clinical Chemistry, 36:2117,1990

  35. Oxytocin & vasopressin Wismer Fries et al. (2005) PNAS, 47:17237-40.

  36. Sex differences in the brain • Psychological differences tell us there must be differences in brain structure or function. • However, there are surprisingly few well-established differences and a tendency for significant differences to be published (or publicized) more than negative findings. • Even this widely published figure disagrees with much current “dogma.” L. Cahill Scientific American, 2006

  37. (Purves et al., 2004) Men have bigger brains • Here is the one indisputable difference: • The male brain is 9% larger, throughout the lifespan; a statistically large difference (d=0.9). • But this is comparable to the height difference (8.6%), birth weight (9.4%) & other organs (liver=15%), so relevance is unclear.

  38. frontal lobe parietal lobe temporal lobe occipital lobe Lobe volumes in adolescenceLenroot RK et al. 2007. Sexual dimorphism of brain developmental trajectories during childhood and adolescence. NeuroImage, 36:1065-73.

  39. Corpus callosum • Popularly claimed to be larger in women. • Began with a small 1982 Science study (14 brains), followed by over 100 further studies. • But 1997 meta-analysis found no meaningful differences: male CC is larger, but not if you correct for overall brain size. Bishop & Wahlsten (1997) Sex differences in the human corpus callosum: Myth or Reality? Neurosci. & Biobehav. Revs. 21:581-601.

  40. Is language processing more lateralized in men? Areas of brain activated while subjects listened to a story. Females appear more symmetric in the way they process speech.

  41. Sommer et al. (2008) Meta-analysis

  42. Planum temporaleSommer et al. (2008)

  43. Resting asymmetryLiu et al., n =300

  44. Biswal et al. • Resting fMRI activity from 1,414 subjects, 35 international sites. • Curves depict resting functional connectivity in area under black dot. • Right curves plot the dorsal dot, more strongly activated in males; Left curves are area under pink dot, stronger connectivity in females.

  45. Mental rotation • Stronger in males, from birth onward, but difference grows through childhood. • The one study of children found no difference between boys and girls, using same MR task that revealed a difference between adults (Kucian et al. 2007). ♂ ♀ Hagdahl et al. (2006)

  46. Brain Fallacy • When most people see sex differences in the brain, they assume that “biology” = “innate.” • In truth, sex differences in the adult brain do not reveal their cause (nature or nurture), because learning and socialization also change the brain.

  47. Hippocampal plasticity in London taxi driversMaguire et al. (2000) PNAS, 97:4398 right hippocampus

  48. Functional imaging(Han & Northoff, 2008) Subject X • Brain activation in two different subjects while performing the same self-judgment task. • Gender learning is at least as potent as other cultural experience in shaping brain & mental function. Subject Y

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