What is Intelligence?
About a century ago, psychologists found that in mental tests designed to measure only domain-specific abilities (such as mathematical ability or memory), people who did well on one kind of test tended to do well on other tests. And those who did poorly, did so across the board. From this overlap, or inter-correlation, it was discovered that there exists a ‘general factor’ which powers (nearly) all mental abilities.
This general factor is called ‘general mental ability,’ ‘general intelligence,’ or simply, intelligence (abbreviated as g). At its core, g can be thought of as ‘brain power’—an individual’s capacity to process information efficiently. An individual with higher g has more ‘brain power.’ Intelligence is thus defined as the capacity to take in, understand and utilize resources in the environment. It so happens that g is the single best predictor of how an individual performs in life at large, and it is for this reason that g is of such profound importance in psychology.
Simply put, intelligence—to a certain extent—determines ‘destiny.’
Intelligence is one of the most heritable traits known. The extent to which genes account for individual differences in intelligence increases with age, from about 40% among preschoolers, 60% by adolescence and to 80% in late adulthood. So-called ‘environmental factors’ like parenting, or level of education have negligible–nil effects on g.
[g is broadly analogous to the performance of the CPU in a computer which acts as the ‘general factor’ that determines the computer’s overall performance. Just as how a CPU’s performance can be graded using a processing benchmark, so too can the ‘human processor.’ IQ tests can be thought of as benchmarks designed to grade an individual’s information processing capabilities.]
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Men have a mean advantage in g of 7 IQ equivalent points along with greater variance in distribution as compared to women. The combined effect of higher mean and greater variance result in an exponentially increasing male over-representation from average g (IQ=100) and up, amounting to 9 males for each female at g=3 SD (IQ=145).
The male advantage in g can be revealed by other psychological tests which tap into an individual’s capacity to process information.
Elementary Cognitive Tasks (ECT) are very basic tasks that have no specific intellectual content, require only a small number of mental processes and have clear correct outcomes. For the same reason, they do not reflect differences in motivation, strategy or personality traits.
- Reaction Time (RT) is one such measure. Not to be confused with “quick reflexes” as in athletics, RT is a measure of cognitive processing speed. Tests of simple RT generally involve pushing a button in response to a stimuli. These are so easy to do that even 10-year-old children can perform them in a second. In aggregate, RTs correlate ~ r=0.70 with g—i.e. intelligent individuals tend to have faster RTs because their brains are more efficient. Men consistently have faster RTs than women despite their larger size.
- Temporal Processing—perception of time—is another measure that correlates ~ r=0.45 with g. From milliseconds, to seconds, to minutes, men perceive time more accurately than women do. A more efficient neurological ‘clock’ reflects faster updation of mental representation cycles in men, positively influencing everything from psychomotor ability (e.g. control precision), to visual processing (e.g. tracking) and, of course, auditory processing.
Nerve Conduction Velocity (NCV) is the speed at which electrical signals propagate down a neural pathway. NCV is moderately correlated with g ~ r=0.35. Men have faster NCVs, increasing with age, despite their larger size.
All of the aforementioned measures reveal that men process information more efficiently than women do. A male mean advantage of about half a standard deviation in IQ points can be computed from a proper battery of ECTs.
Domain Intelligence refers to domain-specific mental abilities such as spatial ability, mathematical ability, verbal ability and psychomotor ability. Men outperform women in most of these measures—a clear indication that there is a male advantage in g, because g is the common factor underlying all these mental abilities.
Unfortunately, this is an extensive topic and will be discussed in a separate article (but some important aspects of this topic are covered in the next section).
Sex-related differences are found at every level of the brain. The most important differences—related to intelligence—are found at the level of organization and may reveal the underlying mechanisms that contribute to the male advantage in general intelligence.
As a general rule, the brain’s structure is an expression of its function, where larger size translates to greater functional capacity. To illustrate this, I take ‘absolute brain size’ as the starting point. Absolute brain size has been established as the best predictor of individual differences in intelligence across species. In humans, absolute brain size is moderately correlated with g ~ r=0.45.
The absolute brain size in men is about 10–12% larger than in women. Males average larger brains from birth and across all age groups—even though girls tend to be taller from ages 10–14. Results from autopsy studies and fMRI find only a weak brain size–body size correlation ~ r=0.20. This means that even after correcting for body size, the brains of men are larger by 8–10%. When brain/body ratios of men and women of equal size are compared, at any given size, the ratio is much higher in men than in women.
Thus, men with their larger brains, have higher g.
Unfortunately, the simplistic presentation of this argument fails to capture its significance, which I will unpack.
Brains may enlarge by adding more neurons, by making existing neurons larger or some combination of both. The most common method of enlargement is by adding more neurons. But, for this to work, the number of connections must increase much faster than the number of neurons in order to maintain connectivity. White matter is known to increase faster than gray matter, but this is not quite fast enough to resolve the connectivity problem. In addition to this design issue, a substantial increase in the ratio of glia–neurons is required to keep up with the increasing energy costs. Given these constraints, brains cannot enlarge without undergoing changes to their organization. Thus, as brains enlarge, they become increasingly modular: larger functions are broken down into smaller processes and processes that handle overlapping tasks are clustered together, enhancing the connectivity within these localized regions.
Then, there’s the other side of the coin: the increase in modularity is further exploited to increase the degree of hemispheric lateralization. ‘Hemispheric lateralization’ is the distribution of functions between the two hemispheres of the brain. The hemispheres have evolved qualitatively different biases in how they interact with each other: the right-hemisphere strongly interacts with both hemispheres whereas the left-hemisphere mostly interacts within itself. This bias is also expressed in their functionality: the right-hemisphere is dominant for ‘global’ information, it operates spatially, intuitively and is concerned with the ‘whole’; the left-hemisphere is dominant for ‘local’ information, it operates verbally, sequentially and is concerned with the constituent ‘parts.’ By distributing functions between the two hemispheres, the brain is able to perform parallel processing. Therefore, as brains enlarge, they become more lateralized to take advantage of enhanced parallel processing.
However, for parallel processing to work, it is necessary to minimise potential conflicts between the hemispheres. The corpus callosum (CC)—the white matter tract connecting the two hemispheres of the brain—functions as the ‘bridge’ between the hemispheres. As brains enlarge, they are optimised for intra-hemispheric connectivity (within-hemisphere) and the CC is scaled down to minimise inter-hemispheric (between-hemisphere) interference.
Putting this all together: larger brains are more modular, more lateralized and consequently, optimised for intra-hemispheric connectivity. Absolute brain size is thus properly understood as a proxy for the brain’s organizational complexity. The end result is a substantial enhancement to parallel processing which leads to a systematic increase in cognitive capacity.
It follows that men’s larger brains are packed with 19% more neocortical neurons for processing, 16% more white matter for connectivity and 28% more neocortical glia to keep up with energy costs. Consequently, men’s brains are more modular, more lateralized and optimised towards an intra-hemispheric configuration whereas women’s brains are more diffused and fall back to an inter-hemispheric configuration. While there are certain benefits to both configurations, the mechanical advantages to men is apparent in task performance:
- Language processing is represented bilaterally in women, but is left-lateralized in men. This necessitates a reliance on inter-hemispheric connectivity in women for processing language, resulting in slower performance and lower verbal intelligence. The intra-hemispheric configuration in men prevents this kind of “traffic jam,” even though they have longer inter-hemispheric transmission times in the left–right direction.
- Women show greater reliance on inter-hemispheric connectivity for non-verbal intelligence as well. Correlations between bi-manual temporal measures, inter-hemispheric transfer times and non-verbal intelligence are significant for women, but not men.
- When adjusted for brain size, women have 3–5% more grey matter than men. This excess, found in the parietal lobe, is associated with a disadvantage in visuospatial processing for women. In contrast, the greater surface area of the parietal lobe in men translates to an advantage.
The sex differences in brain organization manifest in preferred “cognitive styles”—i.e. men and women think differently—the most important aspect of sex differences in intelligence.
Men preferentially engage in a holistic, ‘global’ (“Gestalt”) style of processing taking advantage of their intra-hemispheric connectivity to integrate disparate streams of information into a coherent “whole,” whereas women preferentially engage in a decomposed, ‘local’ style of processing, assembling information piece-by-piece to optimise their reliance on inter-hemispheric connectivity. While there are certain advantages to both cognitive styles, the overall enhancement to cognitive capacity in men cannot be missed:
- Visuospatial ability (VS) is the ability to generate, retain, retrieve, and transform well-structured mental images. VS is a unified trait in men—they are able to integrate complex mental images in a bottom-up, automatic and holistic fashion. For women, VS is a diffused trait—they put together mental images in a top-down, forced and piecemeal fashion. Thus, VS is more of a talent in men and a learned skill for women. Consequently, the more complex the task, the more apparent the male advantage. Incredibly, the male advantage in VS can already be detected in 5-month-old infants.
- The male advantage in VS extends to spatial orientation. Here the global–local bias is immediately evident: when asked to navigate through maps, men focus primarily on global features, such as cardinal directions whereas women focus on local features, such as landmarks. This global–local bias can also be detected in children.
- The male advantage in VS also extends to audiospatial tasks. In binaural auditory processing tasks, the enhanced parallel processing in male brains contribute to a performance advantage.
- The male advantage in VS extends to visuospatial working memory (VSWM). When both object icons and words are presented together for VSWM processing, men outperform women even in the most demanding conditions.
- Mathematical ability is an enhanced trait in men, yet again extending from their advantage in VS. The global bias is also apparent here: the male advantage increases as the level of cognitive complexity increases and also as the content changes from arithmetic through algebra to geometry.
- Temporal Processing—perception of time—also reveals a male advantage. In tasks requiring temporal integration across a series of sensory events, men apply a holistic processing strategy to their advantage.
- Creative thinking is associated with ‘global’ right-hemispheric processing and selective parallel processing. Consequently, there exists a clear male superiority—found cross-culturally—in creativity.
- Men are also more ‘global’ when it comes to ‘social intelligence.’ The male social structure involves complex group-based interactions set up by automatic rank-ordering whereas the female social structure consists of triads, dyads and one-on-one interactions with related individuals. Consequently, men are more competitive, co-operative, collaborative, tolerant of and easily affiliate with genetically unrelated individuals.
The sex difference in ‘cognitive style’ is clearly one of the most profound differences between the sexes, the full extent of which goes well beyond the mere numbers measured by IQ tests (and beyond the scope of this article). It is because IQ tests tap into some of these mechanical differences, that they reveal a higher g score for males.
Thus, men with their more complex brains, have higher g.
Extrapolating from early findings of sex differences in the corpus callosum, it was claimed that because women had a differently shaped corpus callosum, they were better at “multitasking.”
Unfortunately for this claim, the inter-hemispheric setup of the female brain is their primary disadvantage. Even worse for this claim, the human brain is not even capable of true “multitasking.” The closest we come to multitasking is parallel processing, which is an enhanced feature in the male brain. Still worse for this claim, it inadvertently reveals women’s inability to tune out information irrelevant to the task at hand, resulting in sub-optimal performance in certain tasks.
Over the last few years, several publications have put forth claims such as “there are no sex differences in IQ” or that, “women and men are equally intelligent” and even “sex differences in cognitive abilities are small.”
Fully 100% of these publications manufacture their conclusions by either omitting or ignoring critical information regarding sex differences in mental abilities.
Most mental tests are constructed such that items that show a large advantage to one sex are removed, leaving behind a selection of sub-tests that cancel each other out. All popular IQ tests, including the many versions of the Wechsler Adult Intelligence Scales (WAIS), Raven’s Progressive Matrices (RPM) and the Wonderlic Cognitive Ability Test (WCAT) are ‘sex normalized’ in this manner. Since the late ’80s, this treatment has been extended to national and international assessments including the SAT, the Cognitive Abilities Test (CAT), the Programme for International Student Assessment (PISA), the Trends in International Mathematics and Science Study (TIMSS) and even the armed forces’ standardized tests.
[As Namae Nanka pointed out in the comments section, the practice of ‘sex normalization’ has been institutionalized at least since the time of the eminent educational psychologist Lewis Terman.]
It’s ridiculous to claim that sex differences in intelligence are small or non-existent when the tests themselves are constructed to render them invisible. One must look to other measures of intelligence to unveil sex differences in g, such as the ECTs mentioned in the previous section.
It is well known that males tend to show 10–20% greater variance in measures of intellectual capacity, even when mean differences are small. The sex difference in variance is found to emerge even before pre-school, and by age 10, boys have a mean advantage and greater variance. Even among opposite-sex siblings, there are at least two times more males at the extremes. The male tendency to be over-represented at the extremes and the female tendency to crowd around the center of the distribution is a fundamental aspect of sex differences in humans.
Studies that claim there are no sex differences in intellectual capacity tend to ignore these dispersion effects altogether. This is a serious omission which discounts the exponential increase in the proportion of males at higher levels of cognitive ability.
It is well known that boys mature several years after girls do. But the most conspicuous difference is the brain developmental lag seen in males compared to females. The ‘halfway’ point—the transitional point—in brain development for females is age 10.5, whereas the equivalent point for males is age 14.5. Females reach the end of their developmental trajectory at around age 22 and males at around age 30. Furthermore, as I’ve already discussed earlier, the brains of men are organized differently from the brains of women and this results in a substantial difference in processing capacity. Given that brain organization is a function of age, differences in cognitive capacity may not be fully apparent until adulthood.
It is nonsensical to use samples of children in Grades 3–12 to generalize sex differences in intelligence, because it is guaranteed to underestimate the male advantage – by a substantial margin – as such samples contain a much greater proportion of immature males.
There exists a clear and significant male advantage in g that can be revealed by proper testing, but this is hidden through the use of outdated models and incorrect methodology.
One would think that even the most incompetent social scientist would have figured out the critical factors mentioned in the previous section. Indeed, it has now become clear that incompetence is not the problem here—academic fraud of this scale originate from radicals who, disguised as scholars, act in service to misguided ideology.
With the identity politics filtered out:
- Measurable sex differences in general intelligence can largely explain the male dominance in the upper echelons of all known human societies, both in history and in the present day.
- The ‘gender gap’ extends well beyond ‘general intelligence,’ and is most certainly not diminishing. If anything, the proportion of males at the extremes seems to have increased.
- Contrary to various claims, women are not under-represented but over-represented in many domains. As a result of fixed quotas designed to bypass filters for ability, there is now an increasing number of mediocre women and a tragic paucity of gifted individuals in higher educational and S.T.E.M. spheres.
I intend to keep this post updated based on requests and any new data.
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