News Topic gender

A large long-running New Zealand study has found that people who started using cannabis in adolescence and continued to use it for years afterward showed a significant decline in IQ from age 13 to 38. This was true even in those who hadn’t smoked marijuana for some years.

The study has followed a group of 1,037 children born in 1972-73. At age 38, 96% of the 1004 living study members participated in the latest assessment. Around 5% were regularly smoking marijuana more than once a week before age 18 (cannabis use was ascertained in interviews at ages 18, 21, 26, 32, and 38 years, and this group was not more or less likely to have dropped out of the study).

This group showed an average decline in IQ of 8 points on cognitive tests at age 38 compared to scores at age 13. Such a decline was not found in those who began using cannabis after the age of 18. In comparison, those who had never used cannabis showed a slight increase in IQ. The effect was dose-dependent, with those diagnosed as cannabis dependent on three or more occasions showing the greatest decline.

While executive function and processing speed appeared to be the most seriously affected areas, impairment was seen across most cognitive domains and did not appear to be statistically significantly different across them.

The size of the effect is shown by a further measure: informants (nominated by participants as knowing them well) also reported significantly more attention and memory problems among those with persistent cannabis dependence. (Note that a decline of 8 IQ points in a group whose mean is 100 brings it down to 92.)

The researchers ruled out recent cannabis use, persistent dependence on other drugs (tobacco, alcohol, hard drugs), and schizophrenia, as alternative explanations for the effect. The effect also remained after years of education were taken into account.

The finding supports the view that the adolescent brain is vulnerable to the effects of marijuana, and that these effects are long-lasting and significant.

Some numbers for those interested: Of the 874 participants included in the analysis (those who had missed at least 3 interviews in the 25 years were excluded), 242 (28%) never used cannabis, 479 (55%) used it but were never diagnosed as cannabis-dependent, and 153 (17%) were diagnosed on at least one of the interviews as cannabis-dependent. Of these, 80 had been so diagnosed on only one occasion, 35 on two occasions, and 38 on three or more occasions. I note that the proportion of males was significantly higher in the cannabis-dependent groups (39% in never used; 49% in used but never diagnosed; 70%, 63%, 82% respectively for the cannabis-dependent).

Grasp of fractions and long division predicts later math success

One possible approach to improving mathematics achievement comes from a recent study finding that fifth graders' understanding of fractions and division predicted high school students' knowledge of algebra and overall math achievement, even after statistically controlling for parents' education and income and for the children's own age, gender, I.Q., reading comprehension, working memory, and knowledge of whole number addition, subtraction and multiplication.

The study compared two nationally representative data sets, one from the U.S. and one from the United Kingdom. The U.S. set included 599 children who were tested in 1997 as 10-12 year-olds and again in 2002 as 15-17-year-olds. The set from the U.K. included 3,677 children who were tested in 1980 as 10-year-olds and in 1986 as 16-year-olds.

You can watch a short video of Siegler discussing the study and its implications at http://youtu.be/7YSj0mmjwBM.

Spatial skills improve children’s number sense

More support for the idea that honing spatial skills leads to better mathematical ability comes from a new children’s study.

The study found that first- and second-graders with the strongest spatial skills at the beginning of the school year showed the most improvement in their number line sense over the course of the year. Similarly, in a second experiment, not only were those children with better spatial skills at 5 ½ better on a number-line test at age 6, but this number line knowledge predicted performance on a math estimation task at age 8.

Hasty answers may make boys better at math

A study following 311 children from first to sixth grade has revealed gender differences in their approach to math problems. The study used single-digit addition problems, and focused on the strategy of directly retrieving the answer from long-term memory.

Accurate retrieval in first grade was associated with working memory capacity and intelligence, and predicted a preference for direct retrieval in second grade. However, at later grades the relation reversed, such that preference in one grade predicted accuracy and speed in the next grade.

Unlike girls, boys consistently preferred to use direct retrieval, favoring speed over accuracy. In the first and second grades, this was seen in boys giving more answers in total, and more wrong answers. Girls, on the other hand, were right more often, but responded less often and more slowly. By sixth grade, however, the boys’ practice was paying off, and they were both answering more problems and getting more correct.

In other words, while ability was a factor in early skilled retrieval, the feedback loop of practice and skill leads to practice eventually being more important than ability — and the relative degrees of practice may underlie some of the gender differences in math performance.

The findings also add weight to the view being increasingly expressed, that mistakes are valuable and educational approaches that try to avoid mistakes (e.g., errorless learning) should be dropped.

Infants can’t compare big and small groups

Our brains process large and small numbers of objects using two different mechanisms, seen in the ability to estimate numbers of items at a glance and the ability to visually track small sets of objects. A new study indicates that at age one, infants can’t yet integrate those two processes. Accordingly, while they can choose the larger of two sets of items when both sets are larger or smaller than four, they can’t distinguish between a large (above four) and small (below four) set.

In the study, infants consistently chose two food items over one and eight items over four, but chose randomly when asked to compare two versus four and two versus eight.

The researchers suggest that educational programs that claim to give children an advantage by teaching them arithmetic at an early age are unlikely to be effective for this reason.

While the ‘Alzheimer’s gene’ is relatively common — the ApoE4 mutation is present in around 15% of the population — having two copies of the mutation is, thankfully, much rarer, at around 2%. Having two copies is of course a major risk factor for developing Alzheimer’s, and it has been thought that having a single copy is also a significant (though lesser) risk factor. Certainly there is quite a lot of evidence linking ApoE4 carriers to various markers of cognitive impairment.

And yet, the evidence has not been entirely consistent. I have been puzzled by this myself, and now a new finding suggests a reason. It appears there are gender differences in responses to this gene variant.

The study involved 131 healthy older adults (median age 70), whose brains were scanned. The scans revealed that in older women with the E4 variant, brain activity showed the loss of synchronization that is typically seen in Alzheimer’s patients, with the precuneus (a major hub in the default mode network) out of sync with other brain regions. This was not observed in male carriers.

The finding was confirmed by a separate set of data, taken from the Alzheimer's Disease Neuroimaging Initiative database. Cerebrospinal fluid from 91 older adults (average age 75) revealed that female carriers had substantially higher levels of tau protein (a key Alzheimer’s biomarker) than male carriers or non-carriers.

It’s worth emphasizing that the participants in the first study were all cognitively normal — the loss of synchronization was starting to happen before visible Alzheimer’s symptoms appeared.

The findings suggest that men have less to worry about than women, as far as the presence of this gene is concerned. The study may also explain why more women than men get the disease (3 women to 2 men); it is not (although of course this is a factor) simply a consequence of women tending to live longer.

Whether or not these gender differences extend to carriers of two copies of the gene is another story.

A British study looking at possible gender differences in the effects of math anxiety involved 433 secondary school children (11-16 years old) completing customized (year appropriate) mental mathematics tests as well as questionnaires designed to assess math anxiety and (separately) test anxiety. These sources of anxiety are often confounded in research studies (and in real life!), and while they are indeed related, reported correlations are moderate, ranging from .30 to .50.

Previous research has been inconsistent as regards gender differences in math anxiety. While many studies have found significantly greater levels of math anxiety in females, many studies have found no difference, and some have even found higher levels in males. These inconsistencies may stem from differences in how math anxiety is defined or measured.

The present study looked at a rather more subtle question: does the connection between math anxiety and math performance differ by gender? Again, previous research has produced inconsistent findings.

Findings in this study were very clear: while there was no difference between boys and girls in math performance, there were marked differences in both math and test anxiety. Girls showed significantly greater levels of both. Both boys and girls showed a positive correlation between math anxiety and test anxiety, and a negative correlation between math anxiety and math performance, and test anxiety and performance. However, these relationships between anxiety and performance were stronger for girls than boys, with the correlation between test anxiety and performance being only marginally significant for boys (p<0.07), and the correlation between math anxiety and performance disappearing once test anxiety was controlled for.

In other words, greater math anxiety was linked to poorer math performance, but it was significant only for girls. Moreover, anxiety experienced by boys may simply reflect test anxiety, rather than specific math anxiety.

It is worth emphasizing that there was no gender difference in performance — that is, despite laboring under the burden of greater levels of anxiety, the girls did just as well as boys. This suggests that girls might do better than boys if they were free of anxiety. It is possible, however, that levels of anxiety didn’t actually differ between boys and girls — that the apparent difference stems from girls feeling more free to express their anxiety.

However, the finding that anxiety is greater in girls than boys is in line with evidence that anxiety (and worry in particular) is twice as prevalent in women as men, and more support for the idea that the girls are under-performing because of their anxiety comes from another recent study.

In this study, 149 college students performed a relatively simple task while their brain activity was measured. Specifically, they had to identify the middle letter in a series of five-letter groups. Sometimes the middle letter was the same as the other four ("FFFFF") while sometimes it was different ("EEFEE"). Afterward the students completed questionnaires about their anxiety and how much they worry (Penn State Worry Questionnaire and the Anxious Arousal subscale of the Mood and Anxiety Symptom Questionnaire).

Anxiety scores were significantly negatively correlated with accuracy on the task; worry scores were unrelated to performance.

Only girls who identified themselves as particularly anxious or big worriers recorded high brain activity when they made mistakes during the task (reflecting greater performance-monitoring). Although these women performed about the same as others on simple portions of the task, their brains had to work harder at it. Then, as the test became more difficult, the anxious females performed worse, suggesting worrying got in the way of completing the task.

Greater performance monitoring was not evident among anxious men.

[A reminder: these are group differences, and don't mean that all men or all women react in these ways.]

Data from the very large and long-running Cognitive Function and Ageing Study, a U.K. study involving 13,004 older adults (65+), from which 329 brains are now available for analysis, has found that cognitive lifestyle score (CLS) had no effect on Alzheimer’s pathology. Characteristics typical of Alzheimer’s, such as plaques, neurofibrillary tangles, and hippocampal atrophy, were similar in all CLS groups.

However, while cognitive lifestyle may have no effect on the development of Alzheimer's pathology, that is not to say it has no effect on the brain. In men, an active cognitive lifestyle was associated with less microvascular disease. In particular, the high CLS group showed an 80% relative reduction in deep white matter lesions. These associations remained after taking into account cardiovascular risk factors and APOE status.

This association was not found in women. However, women in the high CLS group tended to have greater brain weight.

In both genders, high CLS was associated with greater neuronal density and cortical thickness in Brodmann area 9 in the prefrontal lobe (but not, interestingly, in the hippocampus).

Cognitive lifestyle score is produced from years of education, occupational complexity coded according to social class and socioeconomic grouping, and social engagement based on frequency of contact with relatives, neighbors, and social events.

The findings provide more support for the ‘cognitive reserve’ theory, and shed some light on the mechanism, which appears to be rather different than we imagined. It may be that the changes in the prefrontal lobe (that we expected to see in the hippocampus) are a sign that greater cognitive activity helps you develop compensatory networks, rather than building up established ones. This would be consistent with research suggesting that older adults who maintain their cognitive fitness do so by developing new strategies that involve different regions, compensating for failing regions.

A study involving 75 perimenopausal women aged 40 to 60 has found that those with memory complaints tended to show impairments in working memory and attention. Complaints were not, however, associated with verbal learning or memory.

Complaints were also associated with depression, anxiety, somatic complaints, and sleep disturbance. But they weren’t linked to hormone levels (although estrogen is an important hormone for learning and memory).

What this suggests to me is that a primary cause of these cognitive impairments may be poor sleep, and anxiety/depression. A few years ago, I reported on a study that found that, although women’s reports of how many hot flashes they had didn’t correlate with memory impairment, an objective measure of the number of flashes they experienced during sleep did. Sleep, as I know from personal experience, is of sufficient importance that my rule-of-thumb is: don’t bother looking for any other causes of attention and memory deficits until you have sorted out your sleep!

Having said that, depressive symptoms showed greater relationship to memory complaints than sleep disturbance.

It’s no big surprise to hear that it is working memory in particular that is affected, because what many women at this time of life complain of is ‘brain fog’ — the feeling that your brain is full of cotton-wool. This doesn’t mean that you can’t learn new information, or remember old information. But it does mean that these tasks will be impeded to the extent that you need to hold on to too many bits of information. So mental arithmetic might be more difficult, or understanding complex sentences, or coping with unexpected disruptions to your routine, or concentrating on a task for a long time.

These sorts of problems are typical of those produced by on-going sleep deprivation, stress, and depression.

One caveat to the findings is that the study participants tended to be of above-average intelligence and education. This would protect them to a certain extent from cognitive decline — those with less cognitive reserve might display wider impairment. Other studies have found verbal memory, and processing speed, impaired during menopause.

Note, too, that a long-running, large population study has found no evidence for a decline in working memory, or processing speed, in women as they pass through perimenopause and menopause.

I talked recently about how the well-established difference in spatial ability between men and women apparently has a lot to do with confidence. I also mentioned in passing that previous research has shown that training can close the gender gap. A recent study suggests that this training may not have to be specific to spatial skills.

In the German study, 120 students were given a processing speed test and a standard mental rotation test. The students were evenly divided into three groups: musicians, athletes, and education students who didn’t participate in either sports or music.

While the expected gender gap was found among the education students, the gap was smaller among the sports students, and non-existent in the music students.

Among the education students, men got twice as many rotation problems correct as women. Among the sports students, both men and women did better than their peers in education, but since they were both about equally advantaged, a gender gap was still maintained. However, among the musicians, it was only women who benefited, bringing them up to the level of the men.

Thus, for males, athletes did best on mental rotation; for females, musicians did best.

Although it may be that those who went into music or sports had relevant “natural abilities”, the amount of training in sports/music did have a significant effect. Indeed, analysis found that the advantage of sports and music students disappeared when hours of practice and years of practicing were included.

Interestingly, too, there was an effect of processing speed. Although overall the three groups didn’t differ in processing speed, male musicians had a lower processing speed than female musicians, or male athletes (neither of which groups were significantly different from each other).

It is intriguing that music training should only benefit females’ spatial abilities. However, I’m reminded that in research showing how a few hours of video game training can help females close the gender gap, females benefited from the training far more than men. The obvious conclusion is that the males already had sufficient experience, and a few more hours were neither here nor there. Perhaps the question should rather be: why does sports practice benefit males’ spatial skills? A question that seems to point to the benefits for processing speed, but then we have to ask why sports didn’t have the same effect on women. One possible answer here is that the women had engaged in sports for a significantly shorter time (an average of 10.6 years vs 17.55), meaning that the males tended to begin their sports training at a much younger age. There was no such difference among the musicians.

(For more on spatial memory, see the aggregated news reports)

This is another demonstration of stereotype threat, which is also a nice demonstration of the contextual nature of intelligence. The study involved 70 volunteers (average age 25; range 18-49), who were put in groups of 5. Participants were given a baseline IQ test, on which they were given no feedback. The group then participated in a group IQ test, in which 92 multi-choice questions were presented on a monitor (both individual and group tests were taken from Cattell’s culture fair intelligence test). Each question appeared to each person at the same time, for a pre-determined time. After each question, they were provided with feedback in the form of their own relative rank within the group, and the rank of one other group member. Ranking was based on performance on the last 10 questions. Two of each group had their brain activity monitored.

Here’s the remarkable thing. If you gather together individuals on the basis of similar baseline IQ, then you can watch their IQ diverge over the course of the group IQ task, with some dropping dramatically (e.g., 17 points from a mean IQ of 126). Moreover, even those little affected still dropped some (8 points from a mean IQ of 126).

Data from the 27 brain scans (one had to be omitted for technical reasons) suggest that everyone was initially hindered by the group setting, but ‘high performers’ (those who ended up scoring above the median) managed to largely recover, while ‘low performers’ (those who ended up scoring below the median) never did.

Personality tests carried out after the group task found no significant personality differences between high and low performers, but gender was a significant variable: 10/13 high performers were male, while 11/14 low performers were female (remember, there was no difference in baseline IQ — this is not a case of men being smarter!).

There were significant differences between the high and low performers in activity in the amygdala and the right lateral prefrontal cortex. Specifically, all participants had an initial increase in amygdala activation and diminished activity in the prefrontal cortex, but by the end of the task, the high-performing group showed decreased amygdala activation and increased prefrontal cortex activation, while the low performers didn’t change. This may reflect the high performers’ greater ability to reduce their anxiety. Activity in the nucleus accumbens was similar in both groups, and consistent with the idea that the students had expectations about the relative ranking they were about to receive.

It should be pointed out that the specific feedback given — the relative ranking — was not a factor. What’s important is that it was being given at all, and the high performers were those who became less anxious as time went on, regardless of their specific ranking.

There are three big lessons here. One is that social pressure significantly depresses talent (meetings make you stupid?), and this seems to be worse when individuals perceive themselves to have a lower social rank. The second is that our ability to regulate our emotions is important, and something we should put more energy into. And the third is that we’ve got to shake ourselves loose from the idea that IQ is something we can measure in isolation. Social context matters.

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.

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 3^rd grade, with the ratio of boys to girls in the top 5% rising to 3:1 by 5^th 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, 4^th graders from 38 countries and 8^th 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 8^th 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.

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.

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.

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.

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.

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.

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.

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.

No one is denying that boys are far more likely to be autistic than girls, but a new study has found that this perception of autism as a male disorder also means that girls are less likely to be diagnosed with autistic spectrum disorder (ASD) even when their symptoms are equally severe.

Another factor affecting diagnosis was maternal age — those diagnosed with ASD were likely to have older mothers. It’s suggested that this may be because older mothers are better at identifying their children's difficulties and have more confidence in bringing concerns to the clinic. This is supported by the finding that first-born children were less likely to be diagnosed with ASD, as were children of mothers with depression.

Ethnic origin, maternal class and mother's marital status did not significantly predict a child either having an ASD diagnosis or displaying severe autistic traits.

The findings were based on an analysis of data from a longitudinal UK cohort study, the Avon Longitudinal Study of Parents and Children (ALSPAC).

A meta-analysis of 242 articles assessing the math skills of 1,286,350 people found no difference between the two sexes. This was confirmed in an analysis of the data from several large surveys of American adolescents (the National Longitudinal Surveys of Youth, the National Education Longitudinal Study of 1988, the Longitudinal Study of American Youth, and the National Assessment of Educational Progress).

The issue of “mommy brain” is a complex one. Inconsistent research results make it clear that there is no simple answer to the question of whether or not pregnancy and infant care change women’s brains. But a new study adds to the picture.

Brain scans of 19 women two to four weeks and three to four months after they gave birth showed that grey matter volume increased by a small but significant amount in the midbrain (amygdala, substantia nigra, hypothalamus), prefrontal cortex, and parietal lobe. These areas are involved in motivation and reward, emotion regulation, planning, and sensory perception.

Mothers who were most enthusiastic about their babies were significantly more likely to show this increase in the midbrain regions. The authors speculated that the “maternal instinct” might be less of an instinctive response and more of a result of active brain building. Interestingly, while the brain’s reward regions don’t usually change as a result of learning, one experience that does have this effect is that of addiction.

While the reasons may have to do with genes, personality traits, infant behavior, or present circumstances, previous research has found that mothers who had more nurturing in their childhood had more gray matter in those brain regions involved in empathy and reading faces, which also correlated with the degree of activation in those regions when their baby cried.

A larger study is of course needed to confirm these findings.

Recent rodent studies add to our understanding of how estrogen affects learning and memory. A study found that adult female rats took significantly longer to learn a new association when they were in periods of their estrus cycle with high levels of estrogen, compared to their ability to learn when their estrogen level was low. The effect was not found among pre-pubertal rats. The study follows on from an earlier study using rats with their ovaries removed, whose learning was similarly affected when given high levels of estradiol.

Human females have high estrogen levels while they are ovulating. These high levels have also been shown to interfere with women's ability to pay attention.

On the other hand, it needs to be remembered that estrogen therapy has been found to help menopausal and post-menopausal women. It has also been found to be detrimental. Recent research has suggested that timing is important, and it’s been proposed that a critical period exists during which hormone therapy must be administered if it is to improve cognitive function.

This finds some support in another recent rodent study, which found that estrogen replacement increased long-term potentiation (a neural event that underlies memory formation) in young adult rats with their ovaries removed, through its effects on NMDA receptors and dendritic spine density — but only if given within 15 months of the ovariectomy. By 19 months, the same therapy couldn’t induce the changes.

Because male superiority in mental rotation appears to be evident at a very young age, it has been suggested that testosterone may be a factor. To assess whether females exposed to higher levels of prenatal testosterone perform better on mental rotation tasks than females with lower levels of testosterone, researchers compared mental rotation task scores between twins from same-sex and opposite-sex pairs.

It was found that females with a male co-twin scored higher than did females with a female co-twin (there was no difference in scores between males from opposite-sex and same-sex pairs). Of course, this doesn’t prove that that the differences are produced in the womb; it may be that girls with a male twin engage in more male-typical activities. However, the association remained after allowing for computer game playing experience.

The study involved 804 twins, average age 22, of whom 351 females were from same-sex pairs and 120 from opposite-sex pairs. There was no significant difference between females from identical same-sex pairs compared to fraternal same-sex pairs.

* Please do note that ‘innate male superiority’ does NOT mean that all men are inevitably better than all women at this very specific task! My words simply reflect the evidence that the tendency of males to be better at mental rotation is found in infants as young as 3 months.

Following a monkey study that found training in spatial memory could raise females to the level of males, and human studies suggesting the video games might help reduce gender differences in spatial processing (see below for these), a new study shows that training in spatial skills can eliminate the gender difference in young children. Spatial ability, along with verbal skills, is one of the two most-cited cognitive differences between the sexes, for the reason that these two appear to be the most robust.

This latest study involved 116 first graders, half of whom were put in a training program that focused on expanding working memory, perceiving spatial information as a whole rather than concentrating on details, and thinking about spatial geometric pictures from different points of view. The other children took part in a substitute training program, as a control group. Initial gender differences in spatial ability disappeared for those who had been in the spatial training group after only eight weekly sessions.

Previously:

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.

Another study showing that expert video gamers have improved mental rotation skills, visual and spatial memory, and multitasking skills has led researchers to conclude that training with video games may serve to reduce gender differences in visual and spatial processing, and some of the cognitive declines that come with aging.

A study involving 120 toddlers, tested at 14, 24, and 36 months, has assessed language skills (spoken vocabulary and talkativeness) and the development of self-regulation. Self-regulation is an important skill that predicts later academic and social success. Previous research has found that language skills (and vocabulary in particular) help children regulate their emotions and behavior. Boys have also been shown to lag behind girls in both language and self-regulation.

The present study hoped to explain inconsistencies in previous research findings by accounting for general cognitive development and possible gender differences. It found that vocabulary was more important than talkativeness, and 24-month vocabulary predicted the development of self-regulation even when general cognitive development was accounted for. However, girls seemed ‘naturally’ better able to control themselves and focus, but the ability in boys was much more associated with language skills. Boys with a strong vocabulary showed a dramatic increase in self-regulation, becoming comparable to girls with a strong vocabulary.

These gender differences suggest that language skills may be more important for boys, and that more emphasis should be placed on encouraging young boys to use words to solve problems, rather than accepting that ‘boys will be boys’.

A study involving 2,050 people aged 70 to 89 has found that mild cognitive impairment was 1.5 times more common in men than women. Among the 1,969 who did not have dementia, over 16% (329) had MCI — around 11% amnestic MCI (MCI-A) and 5% non-amnestic (MCI-MCD). A total of 19% of men had MCI, compared to 14% of women. MCI was also more common among the never-married, those with the APOEe4 (Alzheimer’s risk) gene, and those with less education.

This is the first study conducted among community-dwelling persons to find a higher prevalence of MCI in men. However, I note that some years ago I reported on a Dutch study involving some 600 85-year-olds, that found that significantly more women than men had a good memory (41% vs 29%; good mental speed on word and number recognition tests was also found in more women than men: 33% vs 28%). This was considered particularly surprising, given that significantly more of the women had limited formal education compared to the men.

The researchers suggested biological factors such as the relative absence of cardiovascular disease in the women might account for the difference. I would suggest another factor might be social, given that social stimulation has been shown to help prevent cognitive decline, and women are more likely than men to keep up social links in old age.

A number of studies have demonstrated that negative stereotypes (such as “women are bad at math”) can impair performance in tests. Now a new study shows that this effect extends to learning. The study involved learning to recognize target Chinese characters among sets of two or four. Women who were reminded of the negative stereotypes involving women's math and visual processing ability failed to improve at this search task, while women who were not reminded of the stereotype got faster with practice. When participants were later asked to choose which of two colored squares, imprinted with irrelevant Chinese characters, was more saturated, those in the control group were slower to respond when one of the characters had been a target. However, those trained under stereotype threat showed no such effect, indicating that they had not learned to automatically attend to a target. It’s suggested that the women in the stereotype threat group tried too hard to overcome the negative stereotype, expending more effort but in an unproductive manner.

There are two problems here, it seems. The first is that people under stereotype threat have more invested in disproving the stereotype, and their efforts may be counterproductive. The second, that they are distracted by the stereotype (which uses up some of their precious working memory).

A German study involving nearly 4000 older adults (55+) has found that physical activity significantly reduced the risk of developing mild cognitive impairment over a two-year period. Nearly 14% of those with no physical activity at the start of the study developed cognitive impairment, compared to 6.7% of those with moderate activity, and 5.1% of those with high activity. Moderate activity was defined as less than 3 times a week.

In another report, a study involving 1,324 individuals without dementia found those who reported performing moderate exercise during midlife or late life were significantly less likely to have MCI. Midlife moderate exercise was associated with 39% reduction in the odds of developing MCI, and moderate exercise in late life was associated with a 32% reduction. Light exercise (such as bowling, slow dancing or golfing with a cart) or vigorous exercise (including jogging, skiing and racquetball) were not significantly associated with reduced risk for MCI.

And in a clinical trial involving 33 older adults (55-85) with MCI has found that women who exercised at high intensity levels with an aerobics trainer for 45 to 60 minutes per day, four days per week, significantly improved performance on multiple tests of executive function, compared to those who engaged in low-intensity stretching exercises. The results for men were less significant: high-intensity aerobics was associated only with improved performance on one cognitive task, Trail-making test B, a test of visual attention and task-switching.

Consistent with studies showing that gender stereotypes can worsen math performance in females, a year-long study involving 17 first- and second-grade teachers and their 52 boy and 65 girl students has found that boys' math performance was not related to their (female) teacher's math anxiety while girls' math achievement was. Early elementary school teachers in the United States are almost exclusively female. Math achievement was unrelated to teacher math anxiety in both boys and girls at the beginning of the school year. Moreover, achievement was negatively associated with belief in gender stereotypes. Girls who confirmed a belief that boys are better in math than girls scored six points lower in math achievement than did boys or girls who had not developed a belief in the stereotype (102 versus 108). Research has found that elementary education majors have the highest rate of mathematics anxiety of any college major.

A study involving 155 women aged 65-75 has found that those who participated in resistance training once or twice weekly for a year significantly improved their selective attention (maintaining mental focus) and conflict resolution (as well as muscular function of course!), compared to those who participated in twice-weekly balance and tone training. Performance on the Stroop test improved by 12.6% and 10.9% in the once-weekly and twice-weekly resistance training groups respectively, while it deteriorated by 0.5% in the balance and tone group. Improved attention and conflict resolution was also significantly associated with increased gait speed.

A brain scanning study using Pittsburgh Compound B, involving 42 healthy individuals (aged 50-80), of whom 14 had mothers who developed Alzheimer's, 14 had fathers with Alzheimer's, and 14 had no family history of the disease, has found that those with a maternal history had 15% more amyloid-beta plaques than those with a paternal history, and 20% more than those with no family history. The findings add to evidence that having a mother with Alzheimer’s is a greater risk factor than having a father with Alzheimer’s. The groups did not differ in age, gender, education, or apolipoprotein E (ApoE) status.

An analysis technique using artificial neural networks has revealed that the most important factors for predicting whether amnestic mild cognitive impairment (MCI-A) would develop into Alzheimer’s within 2 years were hyperglycemia, female gender and having the APOE4 gene (in that order). These were followed by the scores on attentional and short memory tests.

Why do women tend to be better than men at recognizing faces? Two recent studies give a clue, and also explain inconsistencies in previous research, some of which has found that face recognition mainly happens in the right hemisphere part of the face fusiform area, and some that face recognition occurs bilaterally. One study found that, while men tended to process face recognition in the right hemisphere only, women tended to process the information in both hemispheres. Another study found that both women and gay men tended to use both sides of the brain to process faces (making them faster at retrieving faces), while heterosexual men tended to use only the right. It also found that homosexual males have better face recognition memory than heterosexual males and homosexual women, and that women have better face processing than men. Additionally, left-handed heterosexual participants had better face recognition abilities than left-handed homosexuals, and also tended to be better than right-handed heterosexuals. In other words, bilaterality (using both sides of your brain) seems to make you faster and more accurate at recognizing people, and bilaterality is less likely in right-handers and heterosexual males (and perhaps homosexual women). Previous research has shown that homosexual individuals are 39% more likely to be left-handed.