Part of a series on |
Sex differences in humans |
---|
![]() |
Biology |
Medicine and health |
Neuroscience and psychology |
Sociology and society |
Sex differences in human intelligence have long been a topic of debate among researchers and scholars. It is now recognized that there are no significant sex differences in average IQ, [1] [2] though performance in certain cognitive tasks varies somewhat between sexes. [3] [4]
While some test batteries show slightly greater intelligence in males, others show slightly greater intelligence in females. [3] [4] In particular, studies have shown female subjects performing better on tasks related to verbal ability, [1] and males performing better on tasks related to rotation of objects in space, often categorized as spatial ability. [5]
Some research indicates that male advantages on some cognitive tests are minimized when controlling for socioeconomic factors. [4] It has also been hypothesized that there is slightly higher variability in male scores in certain areas compared to female scores, leading to males' being over-represented at the top and bottom extremes of the distribution, though the evidence for this hypothesis is inconclusive. [6]
There is no statistically significant difference between the average IQ scores of men and women. [1] [7] [4] [8] Average differences have been reported, however, on some tests of mathematics and verbal ability in certain contexts. [4] [9] [5] Some studies have suggested that there may be more variability in cognitive ability among males than among females, [9] but others have contradicted this, [10] or presented evidence that differential variability is culturally rather than biologically determined. [11] According to psychologist Diane Halpern, "there are both differences and similarities in the cognitive abilities of women and men, but there is no data-based rationale to support the idea that either is the smarter or superior sex." [2]
Although most tests show no sex difference, there are some that do. For example, it has been found that female subjects tend to perform better on tests of verbal abilities and processing speed while males tend to perform better on tests of visual-spatial ability and crystallized intelligence. [12] [13] For verbal fluency, females have been specifically found to perform slightly better, on average, in vocabulary and reading comprehension and significantly higher in speech production and essay writing. [14] Males have been specifically found to perform better, on average, in spatial visualization, spatial perception, and mental rotation. [14] None of these findings, however, suggest an advantage for either sex in general intelligence, [13] nor in fluid intelligence. [12]
Most studies find either a very small difference or no sex difference with regard to general intelligence. [3] [15] In 2000, researchers Roberto Colom and Francisco J. Abad conducted a large study of 10,475 adults on five IQ tests taken from the Primary Mental Abilities and found negligible or no significant sex differences. The tests conducted were on vocabulary, spatial rotation, verbal fluency and inductive reasoning. [15]
The literature on sex differences in intelligence has produced inconsistent results due to the type of testing used, and this has resulted in debate among researchers. [16] Garcia (2002) argues that there might be a small insignificant sex difference in intelligence in general (IQ) but this may not necessarily reflect a sex difference in general intelligence or g factor. [16] Although most researchers distinguish between g and IQ, those that argued for greater male intelligence asserted that IQ and g are synonymous (Lynn & Irwing 2004) and so the real division comes from defining IQ in relation to g factor. In 2008, Lynn and Irwing proposed that since working memory ability correlates highest with g factor, researchers would have no choice but to accept greater male intelligence if differences on working memory tasks are found. As a result, a neuroimaging study published by Schmidt (2009) conducted an investigation into this proposal by measuring sex differences on an n-back working memory task. The results found no sex difference in working memory capacity, thus contradicting the position put forward by Lynn and Irwing (2008) and more in line with those arguing for no sex differences in intelligence. [16]
A 2012 review by researchers Richard E. Nisbett, Joshua Aronson, Clancy Blair, William Dickens, James Flynn, Diane F. Halpern and Eric Turkheimer discussed Arthur Jensen's 1998 studies on sex differences in intelligence. Jensen's tests were significantly g-loaded but were not set up to get rid of any sex differences (read differential item functioning ). They summarized his conclusions finding "No evidence was found for sex differences in the mean level of g or in the variability of g. Males, on average, excel on some factors; females on others." Jensen's conclusion that no overall sex differences existed for g has been reinforced by researchers who analyzed this issue with a battery of 42 mental ability tests among adults and found no sex difference. [13]
A large analysis by five researchers with a representative sample size of over 15,000 participants found no support for sex differences in IQ, neither among children nor among adults. [17]
A 2022 meta-analysis found that even small sex-based differences in general intelligence among school-aged children were an artifact of older tests, with current test batteries showing no statistically significant difference between the sexes, but that differences in intelligence sub-types such as processing speed (favoring females) and visual-spatial reasoning (favoring males) remained even when controlling for test age. They concluded that their analysis confirmed previous findings where "no evidence was found for gender differences in the mean level of g or in the variability of g." [12]
Some studies have identified the degree of IQ variance as a difference between males and females. Some researchers have argued that males tend to show greater variability on many traits, a view which is termed the variability hypothesis; for example, having both highest and lowest scores on tests of cognitive abilities. [9] Other research has been published which contradicts this hypothesis, however, showing either equal variability between the sexes in some cultural contexts or else greater representation of females at the upper extreme of some measures of cognitive ability. [6]
Feingold (1992) and Hedges and Nowell (1995) reported that, despite average sex differences being small and relatively stable over time, test score variances of males were generally larger than those of females. [18] Feingold "found that males were more variable than females on tests of quantitative reasoning, spatial visualisation, spelling, and general knowledge. ... Hedges and Nowell go one step further and demonstrate that, with the exception of performance on tests of reading comprehension, perceptual speed, and associative memory, more males than females were observed among high-scoring individuals." [18]
In regards to variability in mathematics performance, a meta-analysis by Lindberg et al. (2010) found male-to-female variance ratios ranged from 0.88 to 1.34 across studies with an average of 1.07, indicating nearly equivalent male and female variances. [10] The authors note that greater male variability is not ubiquitous, and ratios less than 1.0 have been reported in some national and international data sets. [10] A review by Hyde et al. (2009) also evaluated the topic of greater male variability in mathematics performance. [11] The review found that the gender gap among the highest performers has narrowed over time in the U.S., is not found among some ethnic groups and in some nations, and correlates with several measures of gender inequality. [11] The authors conclude that greater male variability in math performance is largely an artifact of cultural factors as opposed to innate biological sex differences. [11]
Differences in brain physiology between sexes do not necessarily relate to differences in intellect. Although men have larger brains, men and women have equal IQs. [19] For men, the gray matter volume in the frontal and parietal lobes correlates with IQ; for women, the gray matter volume in the frontal lobe and Broca's area (which is used in language processing) correlates with IQ. [20] Women have greater cortical thickness, cortical complexity and cortical surface area (controlling for body size) which compensates for smaller brain size. [21] Meta-analysis and studies have found that brain size explains 6–12% of variance among individual intelligence and cortical thickness explains 5%. [22]
Although a meta-analysis of 148 samples from over 8000 participants reported a weak correlation between brain size and IQ, [22] men and women did not differ in IQ, and the researchers concluded that "it is not warranted to interpret brain size as an isomorphic proxy of human intelligence differences." [22] Brain volume contributes little to IQ test performance. Outside of comparing intelligence levels of the sexes, brain size is only one of numerous factors that influence intelligence, alongside white matter integrity, overall developmental stability, parieto-frontal neuronal networks, neuronal efficiency, and cortical gyrification. Brain structural integrity seems to be more important as a biological basis. [22]
In 2021, Lise Eliot et al found no difference in overall male/female abilities in verbal, spatial or emotion processing. [23]
Across countries, males have performed better on mathematics tests than females, but there is the possibility male-female difference in math scores is related to gender inequality in social roles. [7] Some psychologists believe that many historical and current sex differences in mathematics performance may be related to boys' higher likelihood of receiving math encouragement than girls. Parents were, and sometimes still are, more likely to consider a son's mathematical achievement as being a natural skill while a daughter's mathematical achievement is more likely to be seen as something she studied hard for. [24] This difference in attitude may discourage girls and women from further involvement in mathematics-related subjects and careers. [24]
In a 2008 study paid for by the National Science Foundation in the United States, researchers found that girls perform as well as boys on standardized math tests. They attributed this to girls now taking as many advanced math courses as boys, unlike in the past. [25] [26]
There is also evidence that boys are over-represented among the very best and very worst performers on measures of mathematical ability and standardized measures of IQ. [25] Some research suggests that differences in mathematics course performance measures favor females. [27] A small performance difference in mathematics on the SAT [28] persists in favor of males, though the gap has shrunk from 40 points (5.0%) in 1975 [29] to 18 points (2.3%) in 2020. [30] However, the SAT is not a representative sample, given that it tests only college-bound students, and more women than men have attended college since the 1990s. [31] Conversely, the international PISA exam provides representative samples. On the 2018 math PISA, there was no statistically significant difference between the performances of girls and boys in 39.5% of the 76 countries that participated. Meanwhile, boys outperformed girls in 32 countries (42.1%), while girls outperformed boys in 14 (18.4%). [32] On average, boys performed 5 points (1%) higher than girls. However, overall, the gender gap in math and science for boys and girls from similar socio-economic backgrounds was not significant. [32]
On the math portion of the 2019 TIMMS, taken at a similar age as the PISA, girls outperformed boys by 3 points on average, although the difference was not statistically significant. [33] A meta-analysis of nearly half a million participants using data from both the TIMMS and the PISA found that differences were negligible, although girls outperfomed boys in some countries and the opposite occurred in others. [34]
A 2008 meta-analysis published in Science using data from over 7 million students found no statistically significant differences between the mathematical capabilities of males and females. [35] A 2011 meta-analysis with 242 studies from 1990 to 2007 involving 1,286,350 people found no overall sex difference of performance in mathematics. The meta-analysis also found that although there were no overall differences, a small sex difference that favored males in complex problem solving was still present in high school. However, the authors note that boys continue to take more physics courses than girls, which train complex solving abilities and may provide stronger training than pure mathematics. [10]
The mathematics GCSE examination results in England have often been inconsistent about which sex performed better. In 2008, 14.7% of females scored an A or above, while only 13.9% of males did the same. But in 2024, only 15.5% of females scored an A or above, while 18% of males did. [36] A 2020 analysis of gender differences in the mathematical abilities of 13 million students in Italy found that males performed better at mathematics and that this difference appeared to increase the richer the Italian regions were, which is also characterized by greater gender equality. [37]
One line of inquiry has focused on the role that stereotype threat might play in mathematics performance differences between male and female test-takers. [27] Systematic reviews and meta-analyses suggest that stereotype threat is implicated in performance differences on some mathematics tests, though the effect appears to vary considerably in different social contexts and for different test conditions. [38] [39] [40] [41] [42]
Studies have shown a female advantage in reading and verbal skills. [43] [44] On the international PISA reading exam, girls consistently outperform boys across all countries, and all differences are statistically significant. In the most recent PISA exam (2018), girls outperformed boys by almost 30 points. [45] On average in OECD countries, 28% of boys did not obtain a reading proficiency level of 2.
Studies have shown that girls spend more time reading than boys and read more for fun, likely contributing to the gap. [46] Some psychologists believe that many historical and current sex differences in mathematics performance may be related to girls' higher likelihood of receiving reading encouragement than boys. Parents were, and sometimes still are, more likely to consider a daughter's reading achievement as being a natural skill while a son's reading achievement is more likely to be seen as something he studied hard for. [24]
Meta-studies show a male advantage in mental rotation, assessing horizontality and verticality, and a male advantage for most aspects of spatial memory. [47] [48] [49] Women have an advantage for certain components of spatial memory. Whereas men show a selective advantage for fine-grained metric positional reconstruction, where absolute spatial coordinates are emphasized, women show an advantage in spatial location memory, which is the ability to accurately remember relative object positions (where objects are); [48] [50] [51] however, the advantage in spatial location memory is small and inconsistent across studies. [51]
A proposed evolutionary hypothesis is that men and women evolved different mental abilities to adapt to their different roles, including labor-based roles, in society. [51] For example, "ancestral women more often foraged for fruits, vegetables, and roots over large geographic regions." [51] The labor-based role explanation suggests that men may have evolved greater spatial abilities as a result of behaviors such as navigating during a hunt. [52]
Sex differences in mental rotation and judgement of line angles in favor of males have been observed across multiple nations, lending credence to biological origins, though countries with greater gender equality also had greater gaps in these areas, lending credence to possible social influence as well. [53]
Results from studies conducted in the physical environment are not conclusive about sex differences. Various studies on the same task show no differences. There are studies that show no difference in finding one's way between two places. [54]
Performance in mental rotation and similar spatial tasks is affected by gender expectations. [55] For example, studies show that being told before the test that men typically perform better, or that the task is linked with jobs like aviation engineering typically associated with men versus jobs like fashion design typically associated with women, will negatively affect female performance on spatial rotation and positively influence it when subjects are told the opposite. [56]
Playing computer or video games increases mental rotation ability, especially for females. [57] Playing action video games in particular benefits spatial abilities in females more than in males, up to a point where sex differences in spatial attention are eliminated. [57] Gender generally has an influence on preference of game genre. Action video games such as first-person shooters, adventure games, and sports games are generally preferred by male players, while female players tend to prefer games such as puzzle, card, and platform games. [58] [59]
The possibility of testosterone and other androgens as a cause of sex differences in psychology has been a subject of study, but results have been mixed. A meta-analysis of women who were exposed to unusually high levels of androgens in the womb due to congenital adrenal hyperplasia concluded that there is no evidence of enhanced spatial ability among these individuals. [60] The meta-analysis speculates that average sex differences in some spatial tasks could be partially explained by androgen exposure at a different time of the life span, such as during mini-puberty, or by the different socialization males and females experience. [60] In addition, a meta-analysis showed that, although female-to-male transgender individuals who received testosterone therapy did improve their spatial abilities, male-to-female transgender individuals who took androgen-suppressants also showed an improvement or no deterioration of spatial skills. [61]
A 2014 meta-analysis of sex differences in scholastic achievement published in the journal of Psychological Bulletin found females outperformed males in teacher-assigned school marks throughout elementary, junior/middle, high school and at both undergraduate and graduate university level. [62] The meta-analysis done by researchers Daniel Voyer and Susan D. Voyer was from the University of New Brunswick drew from 97 years of 502 effect sizes and 369 samples stemming from the year 1914 to 2011, and found that the magnitude of higher female performance was not affected by year of publication, thereby contradicting recent claims of "boy crisis" in school achievement. [62]
A 2015 study by researchers Gijsbert Stoet and David C. Geary from the journal of Intelligence reported that girl's overall education achievement is better in 70 percent of all the 47–75 countries that participated in PISA. [63] The study consisting of 1.5 million 15-year-olds found higher overall female achievement across reading, mathematics, and science literacy and better performance across 70% of participating countries, including many with considerable gaps in economic and political equality, and they fell behind in only 4% of countries. [63] Stoet et al. said sex differences in educational achievement are not reliably linked to gender equality. [63]
However, there is some evidence that there is bias in teacher grading against males, although evidence for this is not fully conclusive. [64] [65] [66] [67] According to a global report performed by the OECD of over 60 countries, girls were given higher marks in comparison to boys with the same ability. [68]
Prior to the 20th century, it was a commonly held view that men were intellectually superior to women. [69] [70] Early brain studies comparing mass and volumes between the sexes suggested that women were intellectually inferior because they have smaller and lighter brains. [55] Writer Helen H. Gardener publicly disputed this idea with William A. Hammond, former Surgeon General of the United States Army.
In the 19th century, whether men and women had equal intelligence was seen by many as a prerequisite for the granting of suffrage. [71] Leta Hollingworth argued that women were not permitted to realize their full potential, as they were confined to the roles of child-rearing and housekeeping.
During the early 20th century, the scientific consensus shifted to the view that sex plays no role in intelligence. [72]
In his 1916 study of children's IQs, psychologist Lewis Terman concluded that "the intelligence of girls, at least up to 14 years, does not differ materially from that of boys". He did, however, find "rather marked" differences on a minority of tests. For example, he found boys were "decidedly better" in arithmetical reasoning, while girls were "superior" at answering comprehension questions. He also proposed that discrimination, lack of opportunity, women's responsibilities in motherhood, or emotional factors may have accounted for the fact that few women had careers in intellectual fields. [73] [74]
An intelligence quotient (IQ) is a total score derived from a set of standardized tests or subtests designed to assess human intelligence. Originally, IQ was a score obtained by dividing a person's mental age score, obtained by administering an intelligence test, by the person's chronological age, both expressed in terms of years and months. The resulting fraction (quotient) was multiplied by 100 to obtain the IQ score. For modern IQ tests, the raw score is transformed to a normal distribution with mean 100 and standard deviation 15. This results in approximately two-thirds of the population scoring between IQ 85 and IQ 115 and about 2 percent each above 130 and below 70.
Discussions of race and intelligence – specifically regarding claims of differences in intelligence along racial lines – have appeared in both popular science and academic research since the modern concept of race was first introduced. With the inception of IQ testing in the early 20th century, differences in average test performance between racial groups have been observed, though these differences have fluctuated and in many cases steadily decreased over time. Complicating the issue, modern science has concluded that race is a socially constructed phenomenon rather than a biological reality, and there exist various conflicting definitions of intelligence. In particular, the validity of IQ testing as a metric for human intelligence is disputed. Today, the scientific consensus is that genetics does not explain differences in IQ test performance between groups, and that observed differences are environmental in origin.
Human intelligence is the intellectual capability of humans, which is marked by complex cognitive feats and high levels of motivation and self-awareness. Using their intelligence, humans are able to learn, form concepts, understand, and apply logic and reason. Human intelligence is also thought to encompass their capacities to recognize patterns, plan, innovate, solve problems, make decisions, retain information, and use language to communicate.
The g factor is a construct developed in psychometric investigations of cognitive abilities and human intelligence. It is a variable that summarizes positive correlations among different cognitive tasks, reflecting the assertion that an individual's performance on one type of cognitive task tends to be comparable to that person's performance on other kinds of cognitive tasks. The g factor typically accounts for 40 to 50 percent of the between-individual performance differences on a given cognitive test, and composite scores based on many tests are frequently regarded as estimates of individuals' standing on the g factor. The terms IQ, general intelligence, general cognitive ability, general mental ability, and simply intelligence are often used interchangeably to refer to this common core shared by cognitive tests. However, the g factor itself is a mathematical construct indicating the level of observed correlation between cognitive tasks. The measured value of this construct depends on the cognitive tasks that are used, and little is known about the underlying causes of the observed correlations.
Achievement gaps in the United States are observed, persistent disparities in measures of educational performance among subgroups of U.S. students, especially groups defined by socioeconomic status (SES), race/ethnicity and gender. The achievement gap can be observed through a variety of measures, including standardized test scores, grade point average, dropout rates, college enrollment, and college completion rates. The gap in achievement between lower income students and higher income students exists in all nations and it has been studied extensively in the U.S. and other countries, including the U.K. Various other gaps between groups exist around the globe as well.
Sex differences in psychology are differences in the mental functions and behaviors of the sexes and are due to a complex interplay of biological, developmental, and cultural factors. Differences have been found in a variety of fields such as mental health, cognitive abilities, personality, emotion, sexuality, friendship, and tendency towards aggression. Such variation may be innate, learned, or both. Modern research attempts to distinguish between these causes and to analyze any ethical concerns raised. Since behavior is a result of interactions between nature and nurture, researchers are interested in investigating how biology and environment interact to produce such differences, although this is often not possible.
Catharine Morris Cox Miles was an American psychologist known for her work on intelligence and genius. Born in San Jose, CA, to Lydia Shipley Bean and Charles Ellwood Cox. In 1927 married psychologist Walter Richard Miles. Her sister was classics scholar and Quaker administrator Anna Cox Brinton.
Mental rotation is the ability to rotate mental representations of two-dimensional and three-dimensional objects as it is related to the visual representation of such rotation within the human mind. There is a relationship between areas of the brain associated with perception and mental rotation. There could also be a relationship between the cognitive rate of spatial processing, general intelligence and mental rotation.
Spatial visualization ability or visual-spatial ability is the ability to mentally manipulate 2-dimensional and 3-dimensional figures. It is typically measured with simple cognitive tests and is predictive of user performance with some kinds of user interfaces.
Intelligence: Knowns and Unknowns is a report about scientific findings on human intelligence, issued in 1995 by a task force created by the Board of Scientific Affairs of the American Psychological Association (APA) following the publication of The Bell Curve and the scholarly debate that followed it. The report was subsequently published in the February 1996 issue of the peer-reviewed journal American Psychologist.
The variability hypothesis, also known as the greater male variability hypothesis, is the hypothesis that males generally display greater variability in traits than females do.
Sex differences in education are a type of sex discrimination in the education system affecting both men and women during and after their educational experiences. Men are more likely to be literate on a global average, although higher literacy scores for women are prevalent in many countries. Women are more likely to achieve a tertiary education degree compared to men of the same age. Men tended to receive more education than women in the past, but the gender gap in education has reversed in recent decades in most Western countries and many non-Western countries.
Sexual division of labour (SDL) is the delegation of different tasks between the male and female members of a species. Among human hunter-gatherer societies, males and females are responsible for the acquisition of different types of foods and shared them with each other for a mutual or familial benefit. In some species, males and females eat slightly different foods, while in other species, males and females will routinely share food; but only in humans are these two attributes combined. The few remaining hunter-gatherer populations in the world serve as evolutionary models that can help explain the origin of the sexual division of labour. Many studies on the sexual division of labour have been conducted on hunter-gatherer populations, such as the Hadza, a hunter-gatherer population of Tanzania. In modern day society, sex differences in occupation is seen across cultures, with the tendency that men do technical work and women tend to do work related to care.
Many scholars and policymakers have noted that the fields of science, technology, engineering, and mathematics (STEM) have remained predominantly male with historically low participation among women since the origins of these fields in the 18th century during the Age of Enlightenment.
The neuroscience of sex differences is the study of characteristics that separate brains of different sexes. Psychological sex differences are thought by some to reflect the interaction of genes, hormones, and social learning on brain development throughout the lifespan. A 2021 meta-synthesis led by Lise Eliot found that sex accounted for 1% of the brain's structure or laterality, finding large group-level differences only in total brain volume. A subsequent 2021 led by Camille Michèle Williams contradicted Eliot's conclusions, finding that sex differences in total brain volume are not accounted for merely by sex differences in height and weight, and that once global brain size is taken into account, there remain numerous regional sex differences in both directions. A 2022 follow-up meta-analysis led by Alex DeCasien analyzed the studies from both Eliot and Williams, concluding that "The human brain shows highly reproducible sex differences in regional brain anatomy above and beyond sex differences in overall brain size" and that these differences are of a "small-moderate effect size." A review from 2006 and a meta-analysis from 2014 found that some evidence from brain morphology and function studies indicates that male and female brains cannot always be assumed to be identical from either a structural or functional perspective, and some brain structures are sexually dimorphic.
Sex differences in humans have been studied in a variety of fields. Sex determination generally occurs by the presence or absence of a Y chromosome in the 23rd pair of chromosomes in the human genome. Phenotypic sex refers to an individual's sex as determined by their internal and external genitalia and expression of secondary sex characteristics.
Although there are many physiological and psychological gender differences in humans, memory, in general, is fairly stable across the sexes. By studying the specific instances in which males and females demonstrate differences in memory, we are able to further understand the brain structures and functions associated with memory.
Emotional intelligence (EI) involves using cognitive and emotional abilities to function in interpersonal relationships, social groups as well as manage one's emotional states. It consists of abilities such as social cognition, empathy and also reasoning about the emotions of others.
Sex differences in cognition are widely studied in the current scientific literature. Biological and genetic differences in combination with environment and culture have resulted in the cognitive differences among males and females. Among biological factors, hormones such as testosterone and estrogen may play some role mediating these differences. Among differences of diverse mental and cognitive abilities, the largest or most well known are those relating to spatial abilities, social cognition and verbal skills and abilities.
Female education in STEM refers to child and adult female representation in the educational fields of science, technology, engineering, and mathematics (STEM). In 2017, 33% of students in STEM fields were women.
All the tasks produced a male advantage, except for memory for location, where a female advantage emerged.