Confidence is key to women's spatial skills

March, 2012

A series of experiments has found that confidence fully accounted for women’s poorer performance on a mental rotation task.

One of the few established cognitive differences between men and women lies in spatial ability. But in recent years, this ‘fact’ has been shaken by evidence that training can close the gap between the genders. In this new study, 545 students were given a standard 3D mental rotation task, while at the same time manipulating their confidence levels.

In the first experiment, 70 students were asked to rate their confidence in each answer. They could also choose not to answer. Confidence level was significantly correlated with performance both between and within genders.

On the face of it, these findings could be explained, of course, by the ability of people to be reliable predictors of their own performance. However, the researchers claim that regression analysis shows clearly that when the effect of confidence was taken into account, gender differences were eliminated. Moreover, gender significantly predicted confidence.

But of course this is still just indicative.

In the next experiment, however, the researchers tried to reduce the effect of confidence. One group of 87 students followed the same procedure as in the first experiment (“omission” group), except they were not asked to give confidence ratings. Another group of 87 students was not permitted to miss out any questions (“commission” group). The idea here was that confidence underlay the choice of whether or not to answer a question, so while the first group should perform similarly to those in the first experiment, the second group should be less affected by their confidence level.

This is indeed what was found: men significantly outperformed women in the first condition, but didn’t in the second condition. In other words, it appears that the mere possibility of not answering makes confidence an important factor.

In the third experiment, 148 students replicated the commission condition of the second experiment with the additional benefit of being allowed unlimited time. Half of the students were required to give confidence ratings.

The advantage of unlimited time improved performance overall. More importantly, the results confirmed those produced earlier: confidence ratings produced significant gender differences; there were no gender differences in the absence of such ratings.

In the final experiment, 153 students were required to complete an intentionally difficult line judgment task, which men and women both carried out at near chance levels. They were then randomly informed that their performance had been either above average (‘high confidence’) or below average (‘low confidence’). Having manipulated their confidence, the students were then given the standard mental rotation task (omission version).

As expected (remember this is the omission procedure, where subjects could miss out answers), significant gender differences were found. But there was also a significant difference between the high and low confidence groups. That is, telling people they had performed well (or badly) on the first task affected how well they did on the second. Importantly, women in the high confidence group performed as well as men in the low confidence group.




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Older news items (pre-2010) brought over from the old website

Gender gap in math is culture-based

Data from the Trends in International Mathematics and Science Study and the Programme for International Student Assessment, representing 493,495 students ages 14-16 from 69 countries, have revealed only very small gender differences overall, but marked variation when nations are compared. For example, there are more girls in the top tier in countries such as Iceland, Thailand, and the United Kingdom–and even in certain U.S. populations, such as Asian-Americans. However, despite overall similarities in math skills, boys felt significantly more confident in their abilities than girls did and were more motivated to do well. Furthermore, although some studies have found more males than females scoring above the 95th or 99th percentile, this gender gap has significantly narrowed over time in the U.S. and is not found among some ethnic groups and in some nations. Greater male variability with respect to mathematics, where it exists, correlates with several measures of gender inequality.

[707] Hyde, J S., & Mertz J. E.
(2009).  Gender, culture, and mathematics performance.
Proceedings of the National Academy of Sciences. 106(22), 8801 - 8807.

Else-Quest, N.M., Hyde, J.S. & Linn, M.C. 2010. Cross-national patterns of gender differences in mathematics: A meta-analysis. Psychological Bulletin, 136(1), 103-127.

Positive stereotypes can offset negative stereotype effect

A number of studies have now shown that negative stereotypes can impair cognitive performance, mainly through adding to working memory load. A new study has now shown that this effect can be mitigated by the activation of a positive stereotype. The research takes advantage of the fact that we all belong to several social groups. In this case, the relevant groups were ‘female’ and ‘college student’. As usual, when (subtly) reminded of negative stereotypes for women and math, women performed worse. The interesting thing was that this didn’t happen if women were also made aware that college students performed better at math than non-college students. Moreover, this was reflected in working memory capacity. It seems that, when both a positive and a negative stereotype are offered, people will tend to choose the positive stereotype, and the effects of this will cancel out the negative stereotype. It’s also worth noting how easily these stereotypes are activated: effects could be manipulated simply by subtly changing demographic questions asked before the test (and it is not uncommon that test-takers are first required to answer some demographic questions).

[1381] Rydell, R. J., McConnell A. R., & Beilock S. L.
(2009).  Multiple social identities and stereotype threat: Imbalance, accessibility, and working memory..
Journal of Personality and Social Psychology. 96(5), 949 - 966.

Sex difference on spatial skill test linked to brain structure

It’s been well established that men (as a group) consistently out-perform women on spatial tasks. Research has also established that the parietal lobes in women tend to have proportionally more gray matter. Now a new study shows that the thicker cortex in the parietal lobe in women is associated with poorer mental rotation ability. It also reveals that the surface area of the parietal lobe is increased in men, compared to women, and this is directly related to better performance on mental rotation tasks. It also appears that, perhaps because the brain structure is different between men and women, the way the brain performs the task is different. While men appear able to globally rotate an object in space, women seem to do it piecemeal.

[1159] Koscik, T., O'Leary D., Moser D. J., Andreasen N. C., & Nopoulos P.
(2009).  Sex differences in parietal lobe morphology: Relationship to mental rotation performance.
Brain and Cognition. 69(3), 451 - 459.

Gender gap in spatial skills starts in infancy

On their own, the findings reported above do not answer the question of whether gender differences in spatial ability are biological or cultural, as differences in brain structure and performance can be caused by different experiences during childhood. However, research has repeatedly found a gender difference in mental rotation in children four years and older, and now a new study has found evidence that male superiority in mental rotation is present in infants as young as 5 months old.

[703] Moore, D. S., & Johnson S. P.
(2008).  Mental rotation in human infants: a sex difference.
Psychological Science: A Journal of the American Psychological Society / APS. 19(11), 1063 - 1066.

Gender differences in memory

A series of experiments looking at memory performance in men and women has revealed that women did better at verbal episodic memory tasks, such as remembering words, objects, pictures or everyday events, and men outperformed women in remembering symbolic, non-linguistic information, known as visuospatial processing. But women were again better on tasks that require both verbal and visuospatial processing, such as remembering the location of car keys. Women were also better at remembering faces, especially female faces. They also remembered androgynous faces presented as female more accurately than the androgynous faces presented as male, suggesting the reason is that women pay more attention to female than to male faces. Women also performed better than men in tasks requiring little to no verbal processing, such as recognition of familiar odors. But environmental factors, such as education, seem to influence the magnitude of these sex differences.

[1078] Herlitz, A., & Rehnman J.
(2008).  Sex Differences in Episodic Memory.
Current Directions in Psychological Science. 17(1), 52 - 56.

Review supports mild memory impairment in pregnancy

A review of 14 studies testing the memory performances of more than 1,000 pregnant women, mothers and non-pregnant women, has found that pregnant women performed significantly worse on some, but not all aspects of the test. The hardest tests for the pregnant women were those that involved new or demanding tasks. Regular, well-practiced memory tasks were unlikely to be affected. The impairment wasn’t large — comparable to the modest deficits you'd find when comparing healthy 20-year-olds with healthy 60-year-olds. However, the impairment was sometimes still evident a year after birth (none looked beyond that point).

[876] Henry, J. D., & Rendell P. G.
(2007).  A review of the impact of pregnancy on memory function.
Journal of Clinical and Experimental Neuropsychology. 29(8), 793 - 793.

Stereotype-induced math anxiety robs women's working memory

Another study finds evidence that being told men are better at mathematics undermines women's math performance, and extends it by demonstrating that the anxiety induced by the stereotype mainly reduced the verbal part of working memory, and that this carried over to subsequent (non-math-related) tasks. The accuracy of women exposed to the stereotype was reduced from nearly 90% in a pretest to about 80% after being told men do better in mathematics. Among women not receiving that message, performance actually improved slightly.

[505] Beilock, S. L., Rydell R. J., & McConnell A. R.
(2007).  Stereotype Threat and Working Memory: Mechanisms, Alleviation, and Spillover.
Journal of Experimental Psychology: General. 136(2), 256 - 276.

Gender differences in the brain

Results from an extremely large internet survey looking at sex-linked cognitive abilities, personality traits, interests, sexual attitudes and behavior, as well as physical traits, has found that cognitive abilities decline with age more steeply in men than in women. This effect is independent of sexual orientation. Differences in specific cognitive abilities were also found that did depend on sexual orientation as well as gender. Men scored higher than women on tests of mental rotation and the ability to judge line angles, whereas women scored higher than men on tests of object location memory and word fluency. However, homosexual men's visual-spatial abilities were, on average, lower than those of heterosexual men, and lesbian women's visual-spatial abilities were higher than those of heterosexual women.

[1181] Maylor, E. A., Reimers S., Choi J., Collaer M. L., Peters M., & Silverman I.
(2007).  Gender and sexual orientation differences in cognition across adulthood: age is kinder to women than to men regardless of sexual orientation.
Archives of Sexual Behavior. 36(2), 235 - 249.

[945] Collaer, M. L., Reimers S., & Manning J. T.
(2007).  Visuospatial performance on an internet line judgment task and potential hormonal markers: sex, sexual orientation, and 2D:4D.
Archives of Sexual Behavior. 36(2), 177 - 192.

[905] Peters, M., Manning J., & Reimers S.
(2007).  The Effects of Sex, Sexual Orientation, and Digit Ratio (2D:4D) on Mental Rotation Performance.
Archives of Sexual Behavior. 36(2), 251 - 260.

Sex and prenatal hormones affect cognitive performance

A study involving rhesus macaque monkeys has found that the tendency to use landmarks for navigation is typical only of females. In a situation where they had to navigate an open area to locate highly valued food items in goal boxes, gender or prenatal treatment did not affect how well the monkeys did when both spatial and marker cues were available. When landmarks directly indicated the correct locations but spatial information was unreliable, females performed better than males. Moreover, males whose testosterone exposure had been blocked early in gestation were more able to use the landmarks to navigate than normal males.

[1186] Herman, R. A., & Wallen K.
(2007).  Cognitive performance in rhesus monkeys varies by sex and prenatal androgen exposure.
Hormones and Behavior. 51(4), 496 - 507.

Implicit stereotypes and gender identification may affect female math performance

Relatedly, another study has come out showing that women enrolled in an introductory calculus course who possessed strong implicit gender stereotypes, (for example, automatically associating "male" more than "female" with math ability and math professions) and were likely to identify themselves as feminine, performed worse relative to their female counterparts who did not possess such stereotypes and who were less likely to identify with traditionally female characteristics. Strikingly, a majority of the women participating in the study explicitly expressed disagreement with the idea that men have superior math ability, suggesting that even when consciously disavowing stereotypes, female math students are still susceptible to negative perceptions of their ability.

[969] Kiefer, A. K., & Sekaquaptewa D.
(2007).  Implicit stereotypes, gender identification, and math-related outcomes: a prospective study of female college students.
Psychological Science: A Journal of the American Psychological Society / APS. 18(1), 13 - 18.

Women's math performance affected by theories on sex differences

In a salutary reminder to all researchers into gender and race differences, researchers found that women who received a genetic explanation for female underachievement in math or were reminded of the stereotype about female math underachievement, performed more poorly on math tests than those who received an experiential explanation (such as math teachers treating boys preferentially during the first years of math education) or were led to believe there are no sex differences in math.

[1024] Dar-Nimrod, I., & Heine S. J.
(2006).  Exposure to Scientific Theories Affects Women's Math Performance.
Science. 314(5798), 435 - 435.

Memory problems at menopause

Findings from a study of 24 women approaching menopause have confirmed an earlier study involving over 800 women that found such women are no more likely than anyone else to suffer from memory retrieval problems. However, they did find that the women who complained more about problems with forgetfulness had a harder time learning or "encoding" new information, although they didn’t have actually have an impaired ability to learn new information. Although a larger study is needed to explore this link in more detail, the researchers suggest that stress and emotional upheaval may be responsible for attention failures that mean information isn’t encoded. The researchers did find that most of the women in their study had some sort of mood distress, including symptoms of depression or anxiety (note that this was not a random group, but women who were worried about their memory).

The study was reported at the annual meeting of the International Neuropsychological Society in Boston.

Brain size does matter, but differently for men and women

A study involving the intelligence testing of 100 neurologically normal, terminally ill volunteers, who agreed that their brains be measured after death, found that a bigger brain size is correlated with higher intelligence in certain areas, but there are differences between women and men. Verbal intelligence was clearly correlated with brain size, accounting for 36% of the verbal IQ score, for women and right-handed men — but not for left-handed men. Spatial intelligence was also correlated with brain size in women, but much less strongly, while it was not related at all to brain size in men. It may be that the size or structure of specific brain regions is related to spatial intelligence in men. Brain size decreased with age in men over the age span of 25 to 80 years, suggesting that the well-documented decline in visuospatial intelligence with age is related, at least in right-handed men, to the decrease in cerebral volume with age. However age hardly affected brain size in women.

[1029] Witelson, S. F., Beresh H., & Kigar D. L.
(2006).  Intelligence and brain size in 100 postmortem brains: sex, lateralization and age factors.
Brain: A Journal of Neurology. 129(Pt 2), 386 - 398.

Effect of pregnancy on cognition depends on fetal gender

An intriguing new study may shed light on the conflicting results reported regarding the effect of pregnancy on cognition. The study, which tracked women throughout pregnancy through to postnatal resumption of menstruation, found that there was a significant effect of the sex of the baby on working memory and spatial ability. Women pregnant with boys consistently outperformed women pregnant with girls on these tests.

[1187] Vanston, C. M., & Watson N. V.
(2005).  Selective and persistent effect of foetal sex on cognition in pregnant women.
Neuroreport. 16(7), 779 - 782.

Cognitive effects of binge drinking worse for women

A new study looked at the cognitive effects of binge drinking, which apparently is on the rise in several countries, including Britain and the US. The study involved 100 healthy moderate-to-heavy social drinkers aged between 18 and 30. There were equal numbers of males and females. The study found that female binge drinkers performed worse on the working-memory and vigilance tasks than did the female non-binge drinkers.

[1311] Townshend, J. M., & Duka T.
(2005).  Binge Drinking, Cognitive Performance and Mood in a Population of Young Social Drinkers.
Alcoholism: Clinical and Experimental Research. 29(3), 317 - 325.

The effects of training and age on the spatial-memory gender gap

A study of 90 adult rhesus monkeys found young-adult males had better spatial memory than females, but peaked early. By old age, male and female monkeys had about the same performance. This finding is consistent with reports suggesting that men show greater age-related cognitive decline relative to women. A second study of 22 rhesus monkeys showed that in young adulthood, simple spatial-memory training did not help males but dramatically helped females, raising their performance to the level of young-adult males and wiping out the gender gap.

[1193] Lacreuse, A., Kim C. B., Rosene D. L., Killiany R. J., Moss M. B., Moore T. L., et al.
(2005).  Sex, Age, and Training Modulate Spatial Memory in the Rhesus Monkey (Macaca mulatta)..
Behavioral Neuroscience. 119(1), 118 - 126.

Faster neuron transmission in young males

A study of 186 male and 201 female students (aged 18-25) has found that men's brain cells can transmit nerve impulses 4% faster than women's, probably due to the faster increase of white matter in the male brain during adolescence.

[1034] Reed, E. T., Vernon P. A., & Johnson A. M.
(Submitted).  Confirmation of correlation between brain nerve conduction velocity and intelligence level in normal adults.
Intelligence. 32(6), 563 - 572.

IQ-related brain areas may differ in men and women

An imaging study of 48 men and women between 18 and 84 years old found that, although men and women performed equally on the IQ tests, the brain structures involved in intelligence appeared distinct. Compared with women, men had more than six times the amount of intelligence-related gray matter, while women had about nine times more white matter involved in intelligence than men did. Women also had a large proportion of their IQ-related brain matter (86% of white and 84% of gray) concentrated in the frontal lobes, while men had 90% of their IQ-related gray matter distributed equally between the frontal lobes and the parietal lobes, and 82% of their IQ-related white matter in the temporal lobes. The implications of all this are not clear, but it is worth noting that the volume of gray matter can increase with learning, and is thus a product of environment as well as genes. The findings also demonstrate that no single neuroanatomical structure determines general intelligence and that different types of brain designs are capable of producing equivalent intellectual performance.

[938] Haier, R. J., Jung R. E., Yeo R. A., Head K., & Alkire M. T.
(2005).  The neuroanatomy of general intelligence: sex matters.
NeuroImage. 25(1), 320 - 327.

Estrogen combines with stress to impair memory

A rat study has found that male and female rats performed equally well on a task involving the prefrontal cortex when under no stress, and when highly stressed, both made significant memory errors. But importantly, after exposure to a moderate level of stress, females were impaired, but males were not. When investigated further, it was found that female rats only showed this sensitivity when they were in a high-estrogen phase of their estrus cycle. The estrogen effect was confirmed in a further study using female rats who had had their ovaries removed, thus enabling the researchers to compare the effects of estrogen versus a placebo. These results suggest that high levels of estrogen can act to enhance the stress response, causing greater stress-related cognitive impairments, while providing reassurance that estrogen appears to have no effect on cognitive performance under non-stressful conditions.

[746] Shansky, R. M., Glavis-Bloom C., Lerman D., McRae P., Benson C., Miller K., et al.
(2003).  Estrogen mediates sex differences in stress-induced prefrontal cortex dysfunction.
Mol Psychiatry. 9(5), 531 - 538.

No support for idea that pregnancy affects memory and concentration

A study of pregnant women found many agreed with the popular view that pregnancy affects your memory. However, mental tests during pregnancy and after the birth found no difference between the performance of women who were pregnant and those who were not. It was possible that the affects are too mild to be picked up by the tests, or that the fatigue commonly experienced by women during pregnancy and early motherhood leads women to believe that their memory and concentration are affected.

The research was presented at the British Psychological Society annual conference in Bournemouth.

Women better at recognizing female but not male faces

Women’s superiority in face recognition tasks appears to be due to their better recognition of female faces. There was no difference between men and women in the recognition of male faces.

[671] Lewin, C., & Herlitz A.
(2002).  Sex differences in face recognition--Women's faces make the difference.
Brain and Cognition. 50(1), 121 - 128.

Why women better remember emotional memories

A new brain imaging study reveals gender differences in the encoding of emotional memories. We have long known that women are better at remembering emotional memories, now we can see that the sexes tend to encode emotional experiences in different parts of the brain. In women, it seems that evaluation of emotional experience and encoding of the memory is much more tightly integrated.

[807] Canli, T., Desmond J. E., Zhao Z., & Gabrieli J. D. E.
(2002).  Sex differences in the neural basis of emotional memories.
Proceedings of the National Academy of Sciences of the United States of America. 99(16), 10789 - 10794.

Gender differences in frontal lobe neuron density

A recent study has found that women have up to 15% more brain cell density in the frontal lobe, which controls so-called higher mental processes, such as judgement, personality, planning and working memory. However, as they get older, women appear to shed cells more rapidly from this area than men. By old age, the density is similar for both sexes. It is not yet clear what impact, if any, this difference has on performance.

Witelson, S.F., Kigar, D.L. & Stoner-Beresh, H.J. 2001. Sex difference in the numerical density of neurons in the pyramidal layers of human prefrontal cortex: a stereologic study. Paper presented to the annual Society for Neuroscience meeting in San Diego, US.

Gender differences in neural networks underlying beginning reading

A recent study uses EEG readings to investigate gender differences in the emerging connectivity of neural networks associated with phonological processing, verbal fluency, higher-level thinking and word retrieval (skills needed for beginning reading), in preschoolers. The study confirms different patterns of growth in building connections between boys and girls. These differences point to the different advantages each gender brings to learning to read. Boys favor vocabulary sub-skills needed for comprehension while girls favor fluency and phonic sub-skills needed for the mechanics of reading.

Hanlon, H. 2001. Gender Differences Observed in Preschoolers’ Emerging Neural Networks. Paper presented at Genomes and Hormones: An Integrative Approach to Gender Differences in Physiology, an American Physiological Society (APS) conference held October 17-20 in Pittsburgh.

Boys' and girls' brains process faces differently

Previous research has suggested a right-hemisphere superiority in face processing, as well as adult male superiority at spatial and non-verbal skills (also associated with the right hemisphere of the brain). This study looked at face recognition and the ability to read facial expressions in young, pre-pubertal boys and girls. Boys and girls were equally good at recognizing faces and identifying expressions, but boys showed significantly greater activity in the right hemisphere, while the girls' brains were more active in the left hemisphere. It is speculated that boys tend to process faces at a global level (right hemisphere), while girls process faces at a more local level (left hemisphere). This may mean that females have an advantage in reading fine details of expression. More importantly, it may be that different treatments might be appropriate for males and females in the case of brain injury.

[2541] Everhart, E. D., Shucard J. L., Quatrin T., & Shucard D. W.
(2001).  Sex-related differences in event-related potentials, face recognition, and facial affect processing in prepubertal children.
Neuropsychology. 15(3), 329 - 341.

More women than men do well on memory tests in old age

Researchers from Leiden University tested the mental functioning of 599 Dutch men and women aged 85 years. Good mental speed on word and number recognition tests was found in 33% of the women and 28% of the men. Forty one per cent of the women and 29% of the men had a good memory. This despite the fact that significantly more of the women had limited formal education compared to the men (not surprising given the time in which they grew up). The authors suggested that biological differences - such as the relative absence of cardiovascular disease in elderly women compared with men of the same age - could account for these sex differences in mental decline.

[2615] van Exel, E., Gussekloo J., de Craen A. J. M., Bootsma-van der Wiel A., Houx P., Knook D. L., et al.
(2001).  Cognitive function in the oldest old: women perform better than men.
Journal of Neurology, Neurosurgery & Psychiatry. 71(1), 29 - 32.

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Myths about gender and math performance

January, 2012

Two new reviews debunk several theories for the reasons for gender gaps in math performance.

Is there, or is there not, a gender gap in mathematics performance? And if there is, is it biological or cultural?

Although the presence of a gender gap in the U.S. tends to be regarded as an obvious truth, evidence is rather more equivocal. One meta-analysis of studies published between 1990 and 2007, for example, found no gender differences in mean performance and nearly equal variability within each gender. Another meta-analysis, using 30 years of SAT and ACT scores, found a very large 13:1 ratio of middle school boys to girls at the highest levels of performance in the early 1980s, which declined to around 4:1 by 1991, where it has remained. A large longitudinal study found that males were doing better in math, across all socioeconomic classes, by the 3rd grade, with the ratio of boys to girls in the top 5% rising to 3:1 by 5th grade.

Regardless of the extent of any gender differences in the U.S., the more fundamental question is whether such differences are biological or cultural. The historical changes mentioned above certainly point to a large cultural component. Happily, because so many more countries now participate in the Trends in International Mathematics and Science Study (TIMSS) and the Programme in International Student Assessment (PISA), much better data is now available to answer this question. In 2007, for example, 4th graders from 38 countries and 8th graders from 52 countries participated in TIMSS. In 2009, 65 countries participated in PISA.

So what does all this new data reveal about the gender gap? Overall, there was no significant gender gap in the 2003 and 2007 TIMSS, with the exception of the 2007 8th graders, where girls outperformed boys.

There were, of course, significant gender gaps on a country basis. Researchers looked at several theories for what might underlie these.

Contradicting one theory, gender gaps did not correlate reliably with gender equity. In fact, both boys and girls tended to do better in math when raised in countries where females have better equality. The primary contributor to this appears to be women’s income and rates of participation in the work force. This is in keeping with the idea that maternal education and employment opportunities have benefits for their children’s learning regardless of gender.

The researchers also looked at the more specific hypothesis put forward by Steven Levitt, that gender inequity doesn’t hurt girls' math performance in Muslim countries, where most students attend single-sex schools. This theory was not borne out by the evidence. There was no consistent link between school type and math performance across countries.

However, math performance in the 29 wealthier countries could be predicted to a very high degree by three factors: economic participation and opportunity; GDP per capita; membership of one of three clusters — Middle Eastern (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia); East Asian (Hong Kong, Japan, South Korea, Singapore, Taiwan); rest (Russia, Hungary, Czech Republic, England, Canada, US, Australia, Sweden, Norway, Scotland, Cyprus, Italy, Malta, Israel, Spain, Lithuania, Malaysia, Slovenia, Dubai). The Middle Eastern cluster scored lowest (note the exception of Dubai), and the East Asian the highest. While there are many cultural factors differentiating these clusters, it’s interesting to note that countries’ average performance tended to be higher when students attribute less importance to mastering math.

The investigators also looked at the male variability hypothesis — the idea that males are more variable in their performance, and their predominance at the top is balanced by their predominance at the bottom. The study found however that greater male variation in math achievement varies widely across countries, and is not found at all in some countries.

In sum, the cross-country variability in performance in regard to gender indicates that the most likely cause of any differences lies in country-specific social factors. These could include perception of abilities as fixed vs malleable, attitude toward math, gender beliefs.

Stereotype threat

A popular theory of women’s underachievement in math concerns stereotype threat (first proposed by Spencer, Steele, and Quinn in a 1999 paper). I have reported on this on several occasions. However, a recent review of this research claims that many of the studies were flawed in their methodology and statistical analysis.

Of the 141 studies that cited the original article and related to mathematics, only 23 met the criteria needed (in the reviewers’ opinion) to replicate the original study:

  • Both genders tested
  • Math test used
  • Subjects recruited regardless of preexisting beliefs about gender stereotypes
  • Subjects randomly assigned to experimental conditions

Of these 23, three involved younger participants (< 18 years) and were excluded. Of the remaining 20 studies, only 11 (55%) replicated the original effect (a significant interaction between gender and stereotype threat, and women performing significantly worse in the threat condition than in the threat condition compared to men).

Moreover, half the studies confounded the results by statistically adjusting preexisting math scores. That is, the researchers tried to adjust for any preexisting differences in math performance by using a previous math assessment measure such as SAT score to ‘tweak’ the baseline score. This practice has been the subject of some debate, and the reviewers come out firmly against it, arguing that “an important assumption of a covariate analysis is that the groups do not differ on the covariate. But that group difference is exactly what stereotype threat theory tries to explain!” Note, too, that the original study didn’t make such an adjustment.

So what happens if we exclude those studies that confounded the results? That leaves ten studies, of which only three found an effect (and one of these found the effect only in a subset of the math test). In other words, overwhelmingly, it was the studies that adjusted the scores that found an effect (8/10), while those that didn’t adjust them didn’t find the effect (7/10).

The power of the adjustment in producing the effect was confirmed in a meta-analysis.

Now these researchers aren’t saying that stereotype threat doesn’t exist, or that it doesn’t have an effect on women in this domain. Their point is that the size of the effect, and the evidence for the effect, has come to be regarded as greater and more robust than the research warrants.

At a practical level, this may have led to too much emphasis on tackling this problem at the expense of investigating other possible causes and designing other useful interventions.


Kane, J. M., & Mertz, J. E. (2012). Debunking Myths about Gender and Mathematics Performance. Notices of the AMS, 59(1), 10-21.

[2698] Stoet, G., & Geary D. C.
(2012).  Can stereotype threat explain the gender gap in mathematics performance and achievement?.
Review of General Psychology;Review of General Psychology. No Pagination Specified - No Pagination Specified.



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Deep male voice helps women remember

November, 2011

It seems that what is said by deeper male voices is remembered better by heterosexual women, while memory is impaired for higher male voices. Pitch didn’t affect the memorability of female voices.

I had to report on this quirky little study, because a few years ago I discovered Leonard Cohen’s gravelly voice and then just a few weeks ago had it trumped by Tom Waits — I adore these deep gravelly voices, but couldn’t say why. Now a study shows that woman are not only sensitive to male voice pitch, but this affects their memory.

In the first experiment, 45 heterosexual women were shown images of objects while listening to the name of the object spoken either by a man or woman. The pitch of the voice was manipulated to be high or low. After spending five minutes on a Sudoku puzzle, participants were asked to choose which of two similar but not identical versions of the object was the one they had seen earlier. After the memory test, participants were tested on their voice preferences.

Women strongly preferred the low pitch male voice and remembered objects more accurately when they have been introduced by the deeper male voice than the higher male voice (mean score for object recognition was 84.7% vs 77.8%). There was no significant difference in memory relating to pitch for the female voices (83.9% vs 81.7% — note that these are not significantly different from the score for the deeper male voice).

So is it that memory is enhanced for deeper male voices, or that it is impaired for higher male voices (performance on the female voices suggests the latter)? Or are both factors at play? To sort this out, the second experiment, involving a new set of 46 women, included unmanipulated male and female voices.

Once again, women were unaffected by the different variations of female voices. However, male voices produced a clear linear effect, with the unmanipulated male voices squarely in the middle of the deeper and higher versions. It appears, then, that both factors are at play: deepening a male voice enhances its memorability, while raising it impairs its memorability.

It’s thought that deeper voices are associated with more desirable traits for long-term male partners. Having a better memory for specific encounters with desirable men would allow women to compare and evaluate men according to how they might behave in different relationship contexts.

The voices used were supplied by four young adult men and four young adult women. Pitch was altered through software manipulation. Participants were told that the purpose of the experiment was to study sociosexual orientation and object preference. Contraceptive pill usage did not affect the women’s responses.




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Another challenge to idea that men are better at spatial thinking

October, 2011

A cross-cultural study finds a significant gender difference on a simple puzzle problem for one culture but no gender difference for another. The difference was only partly explained by education.

Here’s an intriguing approach to the long-standing debate about gender differences in spatial thinking. The study involved 1,279 adults from two cultural groups in India. One of these groups was patrilineal, the other matrilineal. The volunteers were given a wooden puzzle to assemble as quickly as they could.

Within the patrilineal group, men were on average 36% faster than women. Within the matrilineal group, however, there was no difference between the genders.

I have previously reported on studies showing how small amounts of spatial training can close the gap in spatial abilities between the genders. It has been argued that in our culture, males are directed toward spatial activities (construction such as Lego; later, video games) more than females are.

In this case, the puzzle was very simple. However, general education was clearly one factor mediating this gender difference. In the patrilineal group, males had an average 3.67 more years of education, while in the matrilineal group, men and women had the same amount of education. When education was included in the statistical analysis, a good part of the difference between the groups was accounted for — but not all.

While we can only speculate about the remaining cause, it is interesting to note that, among the patrilineal group, the gender gap was decidedly smaller among those who lived in households not wholly owned by males (in the matrilineal group, men are not allowed to own property, so this comparison cannot be made).

It is also interesting to note that the men in the matrilineal group were faster than the men in the patrilineal group. This is not a function of education differences, because education in the matrilineal group was slightly less than that of males in the patrilineal group.

None of the participants had experience with puzzle solving, and both groups had similar backgrounds, being closely genetically related and living in villages geographically close. Participants came from eight villages: four patrilineal and four matrilineal.


[2519] Hoffman, M., Gneezy U., & List J. A.
(2011).  Nurture affects gender differences in spatial abilities.
Proceedings of the National Academy of Sciences. 108(36), 14786 - 14788.



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Young binge drinkers less able to learn new verbal information

July, 2011

Binge drinking university students, regardless of gender, performed more poorly on tests of verbal memory, but not on a test of visual memory.

Following animal research indicating that binge drinking damages the hippocampus, and other research showing that this learning and memory center is still developing during adolescence, a new study has investigated the effects of binge drinking on learning in university students. The study, involving 122 Spanish university students (aged 18-20), of whom half engaged in binge drinking, found a clear association between binge drinking and a lower ability to learn new verbal information.

Specifically, binge drinkers were more affected by interference in the Rey Auditory Verbal Learning Test, and remembered fewer words; they also performed worse on the Weschler Memory Scale-3rd ed. (WMS-III) Logical Memory subtest, both on immediate and delayed recall. However, there were no differences between the two groups on the WMS-III Family Pictures subtest (measuring visual declarative memory).

These results persisted even after controlling for other possible confounding variables such as intellectual levels, history of neurological or psychopathological disorders, other drug use, or family history of alcoholism.

The genders were evenly represented in both groups. Interestingly, and in contradiction of some other research, women were not found to be more vulnerable to the neurotoxic effects of binge drinking.


[2298] Parada, M., Corral M., Caamaño‐Isorna F., Mota N., Crego A., Holguín S R., et al.
(Submitted).  Binge Drinking and Declarative Memory in University Students.
Alcoholism: Clinical and Experimental Research.



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Adverse changes in sleep duration associated with cognitive decline in middle-aged adults

May, 2011

A large long-running study has found that middle-aged adults whose night’s sleep had decreased from 6-8 hours or increased from 7-8 hours performed worse on some cognitive tests.

From the Whitehall II study, data involving 5431 older participants (45-69 at baseline) has revealed a significant effect of midlife sleep changes on later cognitive function. Sleep duration was assessed at one point between 1997 and 1999, and again between 2002 and 2004. A decrease in average night’s sleep from 6, 7, or 8 hours was significantly associated with poorer scores on tests of reasoning, vocabulary, and the MMSE. An increase from 7 or 8 hours (but not from 6 hours) was associated with lower scores on these, as well as on tests of phonemic and semantic fluency. Short-term verbal memory was not significantly affected. The magnitude of these effects was equivalent to a 4–7 year increase in age.

Around 8% of participants showed an increase from 7-8 hours of sleep over the five-year period (7.4% of women; 8.6% of men), while around a quarter of women and 18% of men decreased their sleep amount from 6-8 hours. About 58% of men and 50% of women reported no change in sleep duration during the study period. Some 27% of the participants were women.

The optimal amount of sleep (in terms of highest cognitive performance) was 7 hours for women, closely followed by 6 hours. For men, results were similar at 6, 7 and 8 hours.

Analysis took into account age, sex, education and occupational status. The Whitehall II study is a large, long-running study involving British civil servants. Sleep duration was assessed simply by responses to the question "How many hours of sleep do you have on an average week night?"

A very large Chinese study, involving 28,670 older adults (50-85), of whom some 72% were women, also supports an inverted U-shaped association between sleep duration and cognitive function, with 7-8 hours sleep associated with the highest scores on a delayed word recall test.

I would speculate that this finding of an effect of short-term verbal memory (in contrast to that of the Whitehall study) may reflect a group distinction in terms of education and occupation. The Whitehall study is the more homogenous (mostly white-collar), with participants probably averaging greater cognitive reserve than the community-based Chinese study. The findings suggest that memory is slower to be affected, rather than not affected.


Ferrie JE; Shipley MJ; Akbaraly TN; Marmot MG; Kivimäki M; Singh-Manoux A. Change in sleep duration and cognitive function: findings from the Whitehall II study. SLEEP 2011;34(5):565-573.

Xu L; Jiang CQ; Lam TH; Liu B; Jin YL; Zhu T; Zhang WS; Cheng KK; Thomas GN. Short or long sleep duration is associated with memory impairment in older Chinese: the Guangzhou Biobank Cohort Study. SLEEP 2011;34(5):575-580.



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The importance of the cerebellum for intelligence and age-related cognitive decline

March, 2011
  • A new study of older adults indicates atrophy of the cerebellum is an important factor in cognitive decline for men, but not women.

Shrinking of the frontal lobe has been associated with age-related cognitive decline for some time. But other brain regions support the work of the frontal lobe. One in particular is the cerebellum. A study involving 228 participants in the Aberdeen Longitudinal Study of Cognitive Ageing (mean age 68.7) has revealed that there is a significant relationship between grey matter volume in the cerebellum and general intelligence in men, but not women.

Additionally, a number of other brain regions showed an association between gray matter and intelligence, in particular Brodmann Area 47, the anterior cingulate, and the superior temporal gyrus. Atrophy in the anterior cingulate has been implicated as an early marker of Alzheimer’s, as has the superior temporal gyrus.

The gender difference was not completely unexpected — previous research has indicated that the cerebellum shrinks proportionally more with age in men than women. More surprising was the fact that there was no significant association between white memory volume and general intelligence. This contrasts with the finding of a study involving older adults aged 79-80. It is speculated that this association may not develop until greater brain atrophy has occurred.

It is also interesting that the study found no significant relationship between frontal lobe volume and general intelligence — although the effect of cerebellar volume is assumed to occur via its role in supporting the frontal lobe.

The cerebellum is thought to play a vital role in three relevant areas: speed of information processing; variability of information processing; development of automaticity through practice.





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Steep cholesterol decline in older women linked to Alzheimer's risk

February, 2011

A long-running study has found cholesterol levels at in mid-life were not linked to later dementia in women, but marked decline in cholesterol level over the study period was.

Research into the link, if any, between cholesterol and dementia, has been somewhat contradictory. A very long-running Swedish study may explain why. The study, involving 1,462 women aged 38-60 in 1968, has found that cholesterol measured in middle or old age showed no link to dementia, but there was a connection between dementia and the rate of decline in cholesterol level. Those women whose cholesterol levels decreased the most from middle to older age were more than twice as likely to develop dementia as those whose cholesterol levels increased or stayed the same (17.5% compared to 8.9%).After 32 years, 161 women had developed dementia.

Later in life, women with slightly higher body mass index, higher levels of cholesterol and higher blood pressure tend to be healthier overall than those whose weight, cholesterol and blood pressure are too low. But it is unclear whether "too low" cholesterol, BMI and blood pressure are risk factors for dementia or simply signs that dementia is developing, for reasons we do not yet understand.

On the other hand, a recent rat study has found that consuming a high cholesterol diet for five months caused memory impairment, cholinergic dysfunction, inflammation, enhanced cortical beta-amyloid and tau and induced microbleedings — all of which is strikingly similar to Alzheimer's pathology. And this finding is consistent with a number of other studies. So it does seem clear that the story of how exactly cholesterol impacts Alzheimer’s is a complex one that we are just beginning to unravel.

In light of other research indicating that the response of men and women to various substances (eg caffeine) may be different, we should also bear in mind that the results of the Swedish study may apply only to women.




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Effects of caffeine vary with quantity and gender

January, 2011

Two recent studies suggest that caffeine is most effective in boosting your energy and alertness in small doses, and more effective for males.

A study involving 80 college students (34 men and 46 women) between the ages of 18 and 40, has found that those given a caffeinated energy drink reported feeling more stimulated and less tired than those given a decaffeinated soda or no drink. However, although reaction times were faster for those consuming caffeine than those given a placebo drink or no drink, reaction times slowed for increasing doses of caffeine, suggesting that smaller amounts of caffeine are more effective.

The three caffeine groups were given caffeine levels of either 1.8 ml/kg, 3.6 ml/kg or 5.4 ml/kg. The computerized "go/no-go" test which tested their reaction times was given half an hour after consuming the drinks.

In another study, 52 children aged 12-17 drank flattened Sprite containing caffeine at four concentrations: 0, 50 mg, 100 mg or 200 mg. Changes in blood pressure and heart rate were then checked every 10 minutes for one hour, at which point they were given a questionnaire and an opportunity to eat all they wanted of certain types of junk food.

Interestingly, there were significant gender differences, with boys drinking high-caffeine Sprite showing greater increases in diastolic blood pressure (the lower number) than boys drinking the low-caffeine Sprite, but girls being unaffected. Boys were also more inclined to report consuming caffeine for energy or “the rush”, than girls were.

Those participants who ingested the most caffeine also ate more high-sugar snack foods in the laboratory, and reported higher protein and fat consumption outside the lab.


[2047] Howard, M. A., & Marczinski C. A.
(2010).  Acute Effects of a Glucose Energy Drink on Behavioral Control.
Experimental and Clinical Psychopharmacology. 18(6), 553 - 561.

[2074] Temple, J. L., Dewey A. M., & Briatico L. N.
(2010).  Effects of Acute Caffeine Administration on Adolescents.
Experimental and Clinical Psychopharmacology. 18(6), 510 - 520.



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