Perché ci sono così poche economiste?

What is the Right Number of Women? Hints and Puzzles from Cognitive Ability Research Garett Jones

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Parte introduttiva

There is no consensus as to the causes of women’s slow advancement in academic economics. Even after adjusting for factors representing family background or productivity a considerable portion of the gender promotion gap remains unexplained.

IL PROBLEMA

here i focus on the possibility that the low representation of women in economics is partially driven by genetic differences in tastes and abilities between the sexes,

TESI

Particularly in a field like academia, where essentially all employees are above the mean in abilities, variances are likely to be important.

CRUCIALE LA VARIANZA

Some useful surveys include Munger (2007), Allen and Gorski (2002), Zup and Forger( 2002), Pinker (2002), and especially Hyde (2005) and Cahill (2006); the most prominent rebuttal of the views expressed by those authors is Spelke (2005).

LETTERATURA

the combination of analogies from other mammals, early childhood studies, well-documented impacts of sex hormones on brain structure, and the repeated finding of higher means and variances in relevant mental abilities (especially mathematical abilities) in males point toward the very real possibility that men and women differ genetically

I FATTORI RILEVANTI PER LA CONTROVERSIA

evolution as a reason for soft priors

Adaptationism— the concept that gene-carriers quickly adapt to their surrounding circumstances— is at the heart of the modern theory of evolution, and it is difficult to imagine that male and female humans have faced identical circumstances across the millennia. Most obviously, men and women have faced systematically different challenges, framed by the nature of the reproductive cycle.

ADATTAMENTO DIVERSO PER UOMO E DONNA

Indeed, when an economist like Brad DeLong (2005) cleanly lays out the terrible dilemma facing women in academia, he inadvertently lays out an evolutionary dilemma as well… The process of climbing to the top of the professoriate is structured as a tournament, in which the big prizes go to those willing to work the hardest and the smartest from their mid-twenties to their late thirties. Given our society (and our biology), a man can enter this tournament without foreclosing many life possibilities [since he can more easily intertemporally substitute fatherhood]…. But given our society (and our biology), a woman cannot

IL DILEMMA DELL’ACCADEMICA

men face a greater expected payoff to taking big risks in the early parts of their life, and, empirically, men are more likely to engage in risky behavior than women. For men and their genes, there is almost always another day. For women, the trade-off is much crueler.

IL RISCHIO È MASCHIO

Men and women differ by 1 to 2 percent of their genomes, Dr. [David] Page said, which is the same as the difference between a man and a male chimpanzee or between a woman and a female chimpanzee….‘ We all recite the mantra that we are 99 percent identical and take political comfort in it,’ Dr. Page said. ’But the reality is that the genetic difference between males and females absolutely dwarfs all other differences in the human genome.’ (Wade 2003)

DIFFERENZE NEL GENOMA

A final genetic note: The fact that men have only one X-chromosome is a fact too large to omit. A woman has two X chromosomes, so if a particular gene is non-functioning on one X chromosome, then she is very likely to have a functioning copy on her second X-chromosome. A man, by contrast, is in no such luck.

CROMOSOMI

brain anatomy and evidence of sexual differentiation

The findings of Allen and Gorski (2002, 291) appear to sum up the consensus on hormones: “With respect to mammals, high levels of sex hormones— whether secreted by the testes or administered by a scientist— result in masculine brain development.”

ORMONI

Halpern (2000, 180)… “There are many studies in which low testosterone for males and high testosterone for females are associated with better performance on several different spatial tests” (171). Kimura (1999, 122) concludes that “the ‘optimal’ level of T[ estosterone] for spatial ability in humans is that of the normal male with lower levels.” Finally, when older men and older women have received hormone replacement therapy, or when people receive hormone therapy as part of a sex change operation, the “expected cognitive changes occurred” (Kimura 1999, 122).

ORMONI E PERFORMANCE

Economists use these spatial abilities in geometric and topological reasoning, so these differences may help explain why ĝ, the fraction of economists who are female, is below 50%.

ECONOMISTI E ABILITÀ SPAZIALE

The best-documented sexual dimorphism in mammals is in the pre-optic area of the hypothalamus, located just in front of the brain stem. This is about twice as big in human males as in human females— a difference visible to the naked eye— and is involved with reproductive behavior.

DIMORFISMI

The hippocampus, a site related to memory and spatial organization, also differs between the sexes (Cahill 2006); it is larger in human females when adjusted for brain size— a relatively recent finding. The finding is unsurprising since women typically do better on tests of memory retrieval and spatial memory.

HIPPOCAMPUS

So while women typically perform worse on spatial rotation tasks, such as what the letter “F” looks like when rotated in three dimensions, they do better at spatial memory tasks, such as where she put the car keys.

ROTAZIONE E MEMORIA SPAZIALE

men’s brains weigh about 15 percent more than women’s.

PESO DEL CERVELLO

modern MRI scans indicate that within a given sex there is a positive correlation between brain size and IQ score (correlations of 0.3 to 0.4 are common), there is less evidence that men and women differ on average overall intelligence.

DIMENSIONI DEL CERVELLO E IQ

In the neuroscience literature, it’s commonly observed that women’s brains are “more balanced” or “better connected” between left and right hemispheres.

DONNE CON EMISFERI PIÙ CONNESSI

the impacts of fetal hormones on brain development are clear enough that there is little debate in the literature over whether some structural differences between men’s and women’s brains are genetically driven.

ORMONI E CERVELLO

MRI scans show that male and female brains consistently use different structures to solve the same kinds of problems: ‘Every time you do a functional MRI on any test, different parts of the brain light up in men and women,’ says Florence Haseltine,

PROBLEM SOLVING

test scores as an indicator of mental ability

A common observation is that men have greater variability than women. Halpern (2000, 86)… It was consistently found that males were more variable than females in general knowledge, mechanical reasoning, quantitative ability, spatial visualization, and spelling… The high math variances are most relevant: On the SAT-Math, Feingold found that male variances were 20-25% larger for males in the four decades before his study, while on SAT-Verbal scores, male variances were about 5% higher…….

VARIANZA NEI PUNTEGGI DEI TEST

I turn to the ability that is likely most relevant to the economics profession as it currently exists: Mathematical abilities… Jonung and Ståhlberg state in their abstract,“[ W] e find economics to be more akin to mathematics than to the other social sciences.”

ECONOMIA E MATEMATICA

The usual stereotype drawn from the psychological literature is that men are better at math and visuospatial skills than women, especially at the upper end of the distribution. The crucial caveats to this generalization are that women are consistently better (on average) at arithmetic and computation than men,

DIFFERENZE IN MATEMATICA

The fact that women are better at computation is especially intriguing in light of recent changes in the accounting profession: In a field that was formerly male-dominated, more than half of all Bachelor’s degrees in accounting are now conferred on women (Koretz 1997, Briggs 2007).

CONTABILITÀ

according to Kimura (1999): She notes that boys do better on math aptitude tests (with the exception of girls’ superior computation ability), while girls do better on math achievement tests.

MATEMATICA: ATITUDINE E AVANZAMENTO

By way of explanation, Kimura notes (78): Since both aspects of math are taught by the same person, teacherrelated factors are unlikely to be the explanation. Nor do other ‘socialization’ explanations such as gender bias in problem content, math anxiety, parental expectation, and so on, adequately account for the differences.

SPIEGAZIONE: ESCLUSA LA SOCIALITÀ

psychologists indeed have addressed the possibility that their tests are biased: They’ve gone out of their way to write word problems that favor females (e.g., “Martha is making square cookies,” Kimura, 1999, 77) but males still perform better

FORSE IL FRAMING?

One source of evidence on the question of male-female differences is neurological disorders. Many such disorders are more common among men than among women; one that deserves particular attention is autism. Simon BaronCohen and his coauthors (2004, 2005) have theorized that autism is largely an “extreme male mind,”

L’INDIZIO DEI DISORDINI MENTALI. AUTISMO

Another source of data is meta-studies by psychologists. In a survey of meta-studies entitled “The Gender Similarities Hypothesis,” Hyde (2005) collected dozens of meta-studies of gender differences in cognitive abilities and personality traits. Among her findings is that on tests of mental rotation, spatial visualization, and spatial perception, males consistently perform better than females, with a median estimate of 0.44 standard deviations above females. Female advantages on tests of verbal fluency, language, and spelling are of the same order of magnitude. Males are overwhelming more aggressive than females (about 0.5 standard deviations, regardless of measure), and females are more agreeable and (importantly, in my view) more conscientious by about 0.2 standard deviations. The female advantage in conscientiousness is likely of first-order importance, particularly in academia, where tenure-track professors need to be self-starters.

META STUDI SUI CARATTERI

If the men of today actually do have an advantage in spatial ability— an advantage, based on Hyde (2005), that raises their mean 0.5 standard deviation higher than the female mean— and if we temporarily assume that men and women have the same standard deviations on this ability, then, at two standard deviations above the female mean, the ratio of men to women is 2.4: 1; at three standard deviations it’s 4: 1, and at four standard deviations it’s 6.5: 1. Adding in a 5% gender difference in standard deviations (as Deary 2003 found for IQ) raises these ratios to 2.5: 1, 5: 1 and 11: 1, respectively.

QUANTIFICARE LA DIFFERENZA

conclusion

With current scientific understanding, the male-female differences on mathematical skills appear likely to persist, even under plausible social interventions like gender-neutral teaching methods.

POLICY INUTILI

Economics could change itself so that it draws on the skills at which women, on average, excel. A more literary and historical economics, one more driven by verbal fluency and conscientious archival work, would be an economics that created greater opportunities for women.

UNICA VIA: DEVE CAMBIARE LA MATERIA. PIU’ STORIA, MENO ANALISI

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