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The present study investigated gender differences in cognitive abilities for children aged 2–7 years on the German Wechsler Primary and Preschool Scale of Intelligence–Fourth Edition (WPPSI-IV). WPPSI-IV data of 1,042 children (517 girls and 525 boys) were selected from the extended dataset of the German WPPSI-IV standardization sample. First of all, confirmatory factor analyses (CFAs) were used to verify the factor structure of the WPPSI-IV, which was proposed by the test developers. Then, multiple-group confirmatory factor models were implemented to explore measurement invariance across gender. Finally, mean differences in the subtests, index scores, as well as full scale IQ (FSIQ) were analyzed. The second-order three-factor model for age group 2:6–3:11 as well as the second-order five-factor model for age group 4:0–7:7 could be verified. For age group 2:6–3:11, full scalar invariance could be accepted, whereas partial scalar invariance could be established by freeing five nonequivalent subtest intercepts for age group 4:0–7:7. These findings support interpretable comparisons of the WPPSI-IV scores between girls and boys. For age group 4:0–7:7, partial invariance should be taken into account in these comparisons. Furthermore, girls aged 4:0–7:7 showed an advantage in processing speed (PS). Mean scores in any of the other cognitive abilities did not differ between girls and boys in both age groups. These results indicated measurement invariance across gender on the WPPSI-IV, so that the tests measure cognitive abilities in the same way for girls and boys. The current findings showed that gender differences in PS may emerge in early childhood, which might lead to gender differences in later educational skills.

Following the Developmental Theory of Sex Differences, males and females have roughly the same IQ during childhood. However, because females enter puberty earlier their general IQ exceeds that of males during early adolescence, after which males enter puberty. By their late teens, males have a small IQ advantage. To test this model, we administered the SPM+ to a sample of 701 male and 705 female school students aged 10 to 19 years from different schools in the Dhofar Governorate in the Sultanate of Oman. Our results broadly validated Lynn's model, as males scores exceeded those of females from the age of 16 onwards. However, we note that there are also alternative explanations for our findings.

Here we test the developmental theory of sex differences in intelligence using latent modeling. The theory has been recently updated ( Lynn, 2017 ). Based on men's greater average brain volumes and premature maturation in women, the theory predicts an intelligence advantage for women (or null sex differences) in early adolescence, but an advantage for men in late adolescence. The findings reported by Lynn are consistent with the theory, but basic measurement issues were not met. Are we taping the same construct regardless of sex and age and can we provide sound conclusions? We considered 10,335 individuals (4992 boys and 5343 girls) within an age range of 12–18 years. They completed the subtests included in the TEA Ability Battery (BAT-7). Theta scores for each subtest were estimated using a three-parameter logistic Item Response Theory model (3PL IRT). Results fitted properly to invariance criteria across age and sex. Latent estimates for the general factor of intelligence (g) were used for testing the theory. The observed findings were in agreement with the developmental theory: there were null sex differences at 12 years of age, but there was an average difference favoring boys equivalent to 5 IQ points at 18 years of age.

This study examines sex differences in reasoning ability assessed with Raven’s Advanced Progressive Matrices among 2,206 (1001 male and 1205 female) school students aged between 15 and 18 from urban and rural secondary schools in the Minya region of southern Egypt. There are no statistically significant differences in intelligence between males and females up until the age of 15. However, males scored significantly higher than females at the ages of 16, 17 and 18, consistent with Lynn’s developmental theory of sex differences in intelligence. In exploring the Egyptian education system and the social dynamics of the Minya region in more depth, we attempt to find various confounds which might offer explanations for this difference. However, we find that Lynn’s model is the most persuasive.

‘Are there sex differences in intelligence?’ considers the data sets from the Scottish Mental Survey of 1932, the National Longitudinal Survey of Youth from 1979, and the Cognitive Abilities Test 3 sample from 2001–3. All three studies show that there is little evidence of any average difference in intelligence between boys and girls, or young adults. However, for overall general intelligence, there are slightly more girls than boys in these samples around the average scores, and proportionately more males than females at the higher and lower extremes. Among the cognitive domains, a different pattern occurred for verbal reasoning: there were more girls at the higher scores.

Sex differences in intelligence are of great importance with regard to understanding intelligence's underlying evolutionary forces. Previous research in this area has had a strong focus on Western ...

Data are reported for the IQs of men and women university students in South Korea showing that men obtained a higher IQ than women by 3 IQ points on the WAIS-R and by 1.8 IQ points on the Advanced Progressive Matrices. Men showed greater variability than women on both tests. The South Korea students obtained a British-scaled IQ of 112.5, approximately 6 IQ points higher than that of British students.

Lynn argues that sex differences in intelligence and drive (underpinned by testosterone) help to explain sex differences in high achievement. This comment proposes that this view can be developed by looking at Baron-Cohen’s concept of the ‘male brain’, which in its extreme manifestations presents as autism-spectrum disorders. It shows that this personality type — specifically a moderately strongly male brain combined with the outlier high IQ also more common among men — is associated with genius, and so the highest levels of achievement, and is partly a reflection of elevated testosterone. Thus an optimally high level of testosterone, also associated with faster life history strategy, is behind both elevated male drive and a greater ability to innovate, systematize and make important breakthroughs, leading to the highest levels of professional achievement. The comment shows that the ‘male brain’ is independent of intelligence and that even the highest echelons of the ‘oldest profession’ are male dominated, as the male brain model would predict.

The study of sex differences in intelligence reveals a paradox. Data-oriented researchers consistently document reproducible differences, whereas leading textbooks, academics, and media consistently deny them. Perhaps, Lynn’s extensive compilation of data on sex differences (this issue) will solve this paradox.

Richard Lynn’s paper on the existence and the magnitude of sex differences in general intelligence proposes that among adults men have a higher average IQ than women and greater variability, and these contribute to the greater number of men among high achievers. The greater variability of males may be attributable to X-linked transmission of intelligence and/or to higher testosterone that could increase the expression of genes related to neurological development or cognition. Key Words: Intelligence, Sex differences, X-linked inheritance

Scores of a sample of 2,440 male and female Somalian school students aged 8 through 18 years on the Standard Progressive Matrices Plus (SPM+) are reported. The sample obtained a British-scaled IQ of 68. There was no statistically significant difference between the scores of the males and females. The variance was greater among the females than among the males.

It is a paradox that males have a larger average brain size than females, that brain size is positively associated with intelligence, and yet numerous experts have asserted that there is no sex difference in intelligence. This paper presents the developmental theory of sex differences in intelligence as a solution to this problem. This states that boys and girls have about the same IQ up to the age of 15 years but from the age of 16 the average IQ of males becomes higher than that of females with an advantage increasing to approximately 4 IQ points in adulthood.

Richard Lynn’s developmental theory of sex differences in intelligence is evaluated using the administration of the Armed Services Vocational Aptitude Battery in the NLSY79. Score increases between age 15 and age 23 are found to be greater in males than in females, supporting an essential element of the theory. On the other hand, neither the sex differences themselves nor their developmental changes are related in any consistent way to the g loadings of the subtests. Therefore sex differences should not be conceptualized as differences in “general” intelligence (g).

Data for a sample of 18-year-old Applied Science and Social Science students in Libya are reported for intelligence (IQ), emotional intelligence (EI) and educational achievement. Means were significantly higher for Applied Science students than for Social Science students both for IQ and EI. Although males obtained higher means than females on intelligence assessed by the Standard Progressive Matrices, and females obtained higher means than males on emotional intelligence assessed by the Goleman test, the sex differences were very small and did not reach statistical significance. IQ, EI and educational achievement were significantly intercorrelated.

Lynn’s developmental theory of sex differences in intelligence provides one tentative explanation for the observed small male advantage in average IQ scores. Relying on indirect evidence, Lynn suggests that because a) brain size is positively associated with intelligence, and b) men have a larger brain size than women, c) men should have higher average IQ scores than women. However, straightforward evidence obtained using neuroimaging approaches shows that men’s larger brains might be devoted to highly demanding visuospatial processing required by tasks on which they excel. Men’s greater cortical values are not related to the general factor of intelligence (g). This advantage is translated into group abilities and specific skills.

Few topics in psychology have generated as much controversy as sex differences in intelligence. For fluid intelligence, researchers emphasize the high overlap between the ability distributions of males and females, whereas research on sex differences in declarative knowledge often uncovers a male advantage. However, on the level of knowledge domains, a more nuanced picture emerged: while females perform better in health-related topics (e.g., aging, medicine), males outperform females in domains of natural sciences (e.g., engineering, physics). In this paper we show that sex differences vary substantially depending on item sampling. Analyses were based on a sample of n = 3306 German high-school students (Grades 9 and 10) who worked on the 64 declarative knowledge items of the Berlin Test of Fluid and Crystallized Intelligence (BEFKI) assessing knowledge within three broad content domains (science, humanities, social studies). Using two strategies of item sampling—stepwise confirmatory factor analysis and ant colony optimization algorithm—we deliberately manipulate sex differences in multi-group structural equation models. Results show that sex differences considerably vary depending on the indicators drawn from the item pool. Furthermore, ant colony optimization outperforms the simple stepwise selection strategy since it can optimize several criteria simultaneously (model fit, reliability, and preset sex differences). Taken together, studies reporting sex differences in declarative knowledge fail to acknowledge item sampling issues. On a more general stance, handling item sampling hinges on profound considerations of the content of measures.

The authors investigate sex differences in mean scores and variance, in general and specific intelligence, based on raw data from the standardization samples of six cognitive ability measures adapted and normed in Romania. The results show that fewer than 10% of the possible comparisons exhibit sex differences; these differences have a random pattern and are not replicated across measures. The authors conclude that these Romanian data show no support for the sex differences in either mean values or variance of scores which were reported by other studies.

Data are reported for the scores of men and women in the standardization of the American WAIS-IV. Men obtained a significantly higher Full Scale IQ than women by 2.25 IQ points and on the General Ability Index by 4.05 IQ points. Men obtained significantly higher scores on the index IQs of Verbal Comprehension, Perceptual Reasoning and Working Memory, and women obtained a significantly higher score on the Processing Speed index IQ. Men showed greater variability than women on the Full Scale IQ, the General Ability Index and on twelve of the fifteen subtests. Key Words: WAIS-IV, Sex differences, Intelligence, Variability

Considerable data are available about sex differences in intelligence, both at the general (more latent) and the specific (more explicit) levels, in children, adolescents, and adults. However, only a small proportion comes from developing countries, where socio-political conditions and patterns of sexual inequality differ markedly from those observed in developed countries. Comparing sex differences data in intelligence between cultures with contrasting socio-political backgrounds permits examining whether biological factors are behind such sex differences. In an effort towards addressing this, we reviewed and compiled intelligence data from Brazil, and found evidence for a male advantage in adulthood in most dimensions of intelligence. We then analyzed new adult data on three unidimensional IQ tests for the measurement of general intelligence (the g factor), and found evidence of a male advantage in two, but a female advantage in the third. However, scores on two tests appeared to be highly confounded with education level, and once this variable was controlled, the female advantage in one test and the male advantage in another were not noticeable.. In general, our results were mostly in line with the male advantage hypothesis, although this did not appear to be uniformly consistent or of high magnitude in Brazil. Societal implications are discussed. Key words: Intelligence, Sex differences, APM, Progressive Matrices, Brazil.

Results are reported for the intelligence of a sample of 722 10 to 18 year olds in Egypt assessed with the Standard Progressive Matrices. Males obtained significantly higher scores than females at the ages of 16 and 17-18 years, supporting the developmental theory of Lynn that males develop a higher average IQ than females from the age of 16 years into adulthood. The sample obtained a British IQ of 89. Key Words: Intelligence; Sex differences; Progressive Matrices; Egypt

The relationship between sex and creativity remains an unresolved research question. The present study aimed to approach this question through the lens of the developmental theory of sex differences in intelligence, which posits a dynamic pattern of sex differences in intellectual abilities from female superiority in childhood and early adolescence to male superiority starting at 16 years of age. A total of 775 participants from three age groups (i.e., children, adolescents, and emerging adults) completed a 4-year longitudinal study comprising four assessments of creative thinking at 1-year intervals. Creative thinking was assessed with the Test for Creative Thinking-Drawing Production. While the results revealed female superiority in childhood and early adolescence, male superiority was not found in adolescence and emerging adulthood. Rather, greater sex similarities and greater male variability were found based on mean and variability analyses, respectively. This study elucidated the link between sex and creativity by (1) taking a developmental perspective, (2) employing a 4-year longitudinal design in three age groups (i.e., children, adolescents, and emerging adults), and (3) analyzing sex differences based on both mean and variability analyses.

This study focuses on lay conceptions of intelligence. It examined sex and cross-cultural similarities and differences in estimated intelligences and beliefs about intelligence in two countries, Angola and East Timor, within the reversal theory framework. A total of 209 Angolan (109 women and 100 men) and 183 Timorese (89 women and 94 men) students were participated in this study. Participants completed a questionnaire in order to estimate their parents', partners' and own overall intelligence and the 8 reversal multiple intelligences (telic, paratelic, conformist, negativistic, autic mastery, autic sympathy, alloic mastery and alloic sympathy intelligence). Respondents also rated 6 questions about intelligence. Men rated their overall, conformist and autic mastery higher than women. Angolans rated their overall, telic, paratelic, conformist, negativistic, autic mastery, autic sympathy, alloic mastery and alloic sympathy intelligence higher than Timorese. In both countries, fathers have been perceived as more intelligent than mothers, and telic intelligence emerged as a significant predictor of overall intelligence. Principal component analysis of the 8 reversal multiple intelligences yielded one factor. Angolan participants revealed more IQ test experience than Timorese participants. Most of respondents in both countries did not believe in sex differences in intelligence. These findings are discussed by means of cross-cultural literature.

Sex differences on the WISC-R in Chinese children were examined in a sample of 788 aged 12years. Boys obtained a higher mean full scale IQ than girls of 3.75 IQ points, a higher performance IQ of 4.20 IQ points, and a higher verbal IQ of 2.40 IQ points. Boys obtained significantly higher means on the information, picture arrangement, picture completion, block design, and object assembly subtests, while girls obtained a significantly higher mean on coding. The results were in general similar to the sex differences in the United States standardisation sample of the WISC-R. Boys showed greater variability than girls.

A study of sex differences in the intelligence of university students in Thailand tested with the Advanced Progressive Matrices found that men obtained a slightly higher score than women by .08d equivalent to 1.2 IQ points. The sample obtained a British IQ of 103. Key Words: Thailand, Advanced Progressive Matrices, Sex differences, Intelligence

1 IntroductionFor the last century it has been consistently asserted by almost all experts that there is no sex difference in intelligence. For example: "it is now demonstrated by countless and large samples that on the two main general cognitive abilities - fluid and crystallized intelligence - men and women, boys and girls, show no significant differences" (Cattell, 1971, p.131); "males and females do not differ in IQ" (Jensen, 1998, p. 360); "on practically all tests now in use, men and women have equal average scores" (Eysenck, 1981, p. 40); "the consistent story has been that men and women have nearly identical IQs" (Herrnstein & Murray, 1994, p. 275).This consensus that there is no sex difference in intelligence was broken in 1994 when it was contended by the first author that while up to the age of 15 to 16 years males and females do have approximately the same intelligence except for a small male advantage on the visualization abilities, from the age of 16 to 17 years males begin to show greater intelligence reaching an advantage of 4 to 5 IQ points in adults (Lynn, 1994, 1999). The starting point of this new contention was Ankney's (1992) finding that men have a larger average brain size than women, even when this is controlled for body size. Brain size is positively associated with intelligence at a correlation of .40, as shown in the metaanalysis of Vernon et al (2000, p.248), so it was argued that it follows that men should have greater average intelligence than women. The usual counterargument here is that men use their extra brain space for killing, raping and war, rather than general intelligence.As might be expected, the contention that men have a higher average intelligence than women was not received with immediate and universal acceptance. Most experts ignored it and continued to assert that there is no sex difference in intelligence. For instance, Mackintosh (1996, p.567): "there is no sex difference in general intelligence worth speaking of"; Butterworth (1999, p.293): "women's brains are 10% smaller than men's, but their IQ is on average the same"; Bartholomew (2004, p. 91): "men on average have larger brains than women but display no significant advantage in cognitive performance"; Anderson (2004, p. 829): "it is an important finding of intelligence testing that there is no difference between the sexes in average intellectual ability; Hines (2007, p. 103): "there appears to be no sex difference in general intelligence." As recently as 2012, Halpern (2012, p.233) in her book on sex differences in intelligence has written that "Males and females score identically on IQ tests".There have, however, been a few scholars who have addressed the issue and confirmed the claim that men have a higher average intelligence than women. Nyborg (2003) reported a male advantage on g of 5.55 IQ points. Jackson & Rushton (2006) reported that among 100,000 17-18 year olds males have an advantage on g of 3.63 IQ points on the SAT, although here it could be argued that mediocre females are more likely than mediocre males to take the SAT because lower-IQ males tend to be lacking in ambition and have better opportunities for occupational careers that do not require a college education. And Meisenberg (2009) has reported a male advantage of 2.8 IQ points among 22-23 year old whites in the United States on the ASVAB (Armed Services Vocational Aptitude Battery). This difference, however, was not present among blacks. In this study intelligence was also measured as g, and for this there was no significant sex difference among 15 year olds among either blacks or whites, but among whites a significant male advantage of 4 IQ points was present among 16 year olds and this increased to an advantage of 6.5 among 22-23 year olds, while for blacks a male advantage of 1 IQ point was present among 16 year olds and this increased to an advantage 2.15 points among 22-23 year olds.While numerous scholars have continued to state that there are no sex differences in intelligence, the only one who has contested the claim that men have a higher average intelligence than women is Mackintosh (1996). …

This special issue - Evolution of race and sex differences in intelligence and personality: Tribute to Richard Lynn at eighty – testifies to his many research interests over time, where Richard often pioneered. To mention a few examples, he clarified the confusion about the existence of an average sex difference in IQ, by demonstrating that children below 15 do not show the later adult sex difference. More importantly, Richard was the first to establish average IQs for all countries with more than 40.000 people, and then, with Tatu Vanhanen, illustrated the impressive predictive power of these IQs for understanding essential aspects of a nation’s economical and social infrastructure. Richard was also the first to realise that classical eugenic measures do not suffices to avert serious consequences of dysgenics and to suggest that modern reproductive technologies may entail better eugenic potentials. The present conversation provides sufficient details to get a glimpse of the person behind these pioneering efforts this and of his courage. As a prominent member of the London School of Differential Psychology he paints broad consequential strokes on our deeper understanding of human nature and what makes civilizations rise and fall. The behavioural sciences need extraordinary people like him.

This paper presents the results of a longitudinal study of sex differences in intelligence as a test of Lynn’s (1994) hypothesis that from the age of 16 years males develop higher average intelligence than females. The results show that at the ages of 7 and 11 years girls have an IQ advantage of approximately 1 IQ point, but at the age of 16 years this changes in the same boys and girls to an IQ advantage of 1.8 IQ points for boys.

This study investigates whether sex differences in school achievement in three domains are associated with sex differences in intelligence, personality and school-related motivation. In a sample of 1353 Austrian eight graders (552 males, 801 females; mean age 13.74 years, SD = .47), intelligence, the Big Five personality factors as well as domain-specific school anxiety, ability self-perceptions and interests were assessed as predictors of grades in German, Math and English. Most predictors yielded significant mean differences between sexes. Intelligence and ability self-perceptions were the strongest predictors of grades in all domains. In Math, additional predictors of grades were Conscientiousness and Neuroticism. Grades in German and English were also predicted by the interaction between sex and Extraversion. While for girls a higher level of Extraversion was associated with better grades, the opposite was true for boys. Only in German, there was an additional interaction between sex and verbal intelligence indicating that girls benefit even more than boys from a high level of verbal intelligence.

This study is part of a programmatic research effort into the determinants of self-assessed abilities. It examined cross-cultural differences in beliefs about intelligence and self- and other-estimated intelligence in two countries at extreme ends of the European continent. In all, 172 British and 272 Turkish students completed a three-part questionnaire where they estimated their parents', partners' and own multiple intelligences (Gardner (10) and Sternberg (3)). They also completed a measure of the 'big five' personality scales and rated six questions about intelligence. The British sample had more experience with IQ tests than the Turks. The majority of participants in both groups did not believe in sex differences in intelligence but did think there were race differences. They also believed that intelligence was primarily inherited. Participants rated their social and emotional intelligence highly (around one standard deviation above the norm). Results suggested that there were more cultural than sex differences in all the ratings, with various interactions mainly due to the British sample differentiating more between the sexes than the Turks. Males rated their overall, verbal, logical, spatial, creative and practical intelligence higher than females. Turks rated their musical, body-kinesthetic, interpersonal and intrapersonal intelligence as well as existential, naturalistic, emotional, creative, and practical intelligence higher than the British. There was evidence of participants rating their fathers' intelligence on most factors higher than their mothers'. Factor analysis of the ten Gardner intelligences yield two clear factors: cognitive and social intelligence. The first factor was impacted by sex but not culture; it was the other way round for the second factor. Regressions showed that five factors predicted overall estimates: sex (male), age (older), test experience (has done tests), extraversion (strong) and openness (strong). Results are discussed in terms of the growing literature in the field.

This study investigated the possibility that apparent sex differences in IQ are at least partly created by the degree of sample restriction from the baseline population. We used a nationally representative sample, the 1970 British Cohort Study. Sample sizes varied from 6518 to 11,389 between data-collection sweeps. Principal components analysis of scores obtained on four cognitive tests administered at age 10 was used to obtain estimates that we name ‘IQ’. These age-10 scores were then used to estimate the sex differences at age 10, and also among participants in the two later waves, at age 26 and 30. At age 10, there was a small but significant advantage for boys (Cohen’s d = 0.081). Boys had greater variability in these IQ scores. We then investigated how this very small male advantage at 10 changed with sample restriction. We used the same IQs obtained at age 10, but considered only those subjects who returned for data-collection sweeps at ages 26 and 30 years. Subjects returning at age 26 and 30 were more likely to be females and to have higher age-10 IQ scores. Attrition at age 30 was 28% and the male advantage in IQ scores increased by 15%. Attrition at age 26 was 43% and the male advantage in IQ scores increased by 48%. The findings underline the importance of monitoring attrition in longitudinal studies, as well as emphasising the need for representative samples in studying sex differences in intelligence. A proportion of the apparent male advantage in general cognitive ability that has been reported by some researchers might be attributable to the combination of greater male variance in general cognitive ability and sample restriction, though this remains to be tested in a sample with an appropriate mental test battery.

This study investigates the extent to which girls' better school attainment is associated with sex differences in intelligence, personality and school‐related motivation. In a sample of 1353 Austrian pupils (mean age 13.74 years), intelligence, the Big Five of personality, self‐esteem, school anxiety, school‐related intrinsic motivation and achievement goals were assessed as predictors and GPA as achievement criterion. Most predictors yielded significant mean differences between sexes and some of the variables predicted school achievement only for boys or only for girls. Intelligence and self‐esteem were the strongest predictors of GPA for both sexes, and school‐related intrinsic motivation, school anxiety and performance‐avoidance goals explained additional variance in GPA only for boys, whereas work avoidance did so only for girls. Copyright © 2008 John Wiley & Sons, Ltd.

The consensus view states that there are no sex differences in intelligence. However, Lynn (1994, 1999) has formulated a developmental theory of sex differences in intelligence that challenges that view. The theory states that boys and girls mature at different rates such that the growth of girls accelerates at the age of about 9 years and remains in advance of boys until 14–15 years. At 15–16 years the growth of girls decelerates relative to boys. As boys continue to grow from this age their height and their mean IQs increase relative to those of girls. This paper presents new evidence for the theory from the Spanish standardization sample of the fifth edition of the DAT. 1027 boys and 924 girls between 12 and 18 years were tested. The general trend shows that girls do better at the younger ages and their performance declines relative to boys among older age groups, which supports the developmental theory. The sex difference for the DAT as a whole for 18 year olds is a 4.3 IQ advantage for boys, very close to the advantage that can be predicted from their larger brain size (4.4 IQ points). The profile of sex differences in abilities among the Spanish sample is closely similar to that in the United States and Britain, which is testimony to the robustness of the difference in these different cultures.

In 1992, it was reported by Ankney and Rushton that males have larger average brain size than females even when allowance is made for body size. It is known that brain size is associated with intelligence, and it would therefore be expected that males would have higher intelligence than females. Yet it has been universally maintained that there is no difference in intelligence between the sexes. It is proposed that this anomaly can be resolved by a developmental theory of sex differences in intelligence which states that girls mature more rapidly in brain size and neurological development than boys up to the age of 15 years. The faster maturation of girls up to this age compensates for their smaller brain size with the result that sex differences in intelligence are very small, except for some of the spatial abilities. From the age of 16 years onwards, the growth rate of girls decelerates relative to that of boys. The effect of this is that a discernible male advantage of about 4 IQ points develops from the age of 16 into adulthood, consistent with the larger average male brain size. This paper presents new evidence on the developmental theory of sex differences in intelligence and discusses alternative attempts to deal with the anomaly by Ankney (1995), Mackintosh (1996), and Jensen (1998).

Students of the problem of sex differences in intelligence will be indebted to Mackintosh and Flynn for providing useful further clarification of the issue of sex differences in intelligence. I have little to say about Flynn's paper except to note that it confirms my thesis that among adults males have a small advantage over females in abstract reasoning ability. Mackintosh and I have some common ground but there remain substantial disagreements.

Males have larger brains than females, even when corrected for body size, and brain size is positively correlated with intelligence. This leads to the expectation that males should have higher average levels of intelligence than females. Yet the consensus view is that there is no sex difference in general intelligence. An examination of the literature shows that the consensus view is wrong. Among adults, males have slightly higher verbal and reasoning abilities than females and a more pronounced superiority on spatial abilities. If the three abilities are combined to form general intelligence, the mean for males is 4 IQ points higher than the mean for females. Among children up to the age of around 14 yr the sex differences are smaller because girls mature earlier than boys. The evolutionary selection pressures responsible for greater intelligence in males are discussed.

Successful intelligence involves a broader range of abilities than is typically measured by tests of intellectual and academic skills. Most of these tests measure primarily or exclusively memory and analytical abilities. With regard to memory, they assess the abilities to recall and recognize information. With regard to analytical abilities, they measure the skills involved when one analyzes, compares and contrasts, evaluates, critiques, and judges. Several separate factor-analytic studies support the internal validity of the theory of successful intelligence. The theory of successful intelligence is valid as a whole. Moreover, the theory can make a difference not only in laboratory tests but in school classrooms and even the everyday life of adults as well. The educational system in the United States, as in many other countries, places great emphasis on instruction and assessments that tap into two important skills: memory and analysis.

This chapter attempts to broadly outline the current understanding of the etiology of intelligence and intelligence-related processes. First, it describes the major concepts that have primarily guided studies of the etiological bases of intellectual abilities and disabilities. Then, the chapter discusses the state of the field's understanding of cases of intellectual abilities and disabilities. A point of view on the Chinese initiative as presented in the CNN electronic publication is described. The chapter describes the major concepts that have been and are used to explore the connection between the genes and intelligence. The evidence pertaining to observations that the genome is a major source of the variations in individuals' intellectual abilities and disabilities is discussed. Studies of various indicators of information processing speed have been prominent in the field of intelligence due to the observation that these indicators reliably correlate with various aspects of intelligence, especially, with the g factor.

The unification of the fields of mating and intelligence, implied in the mating intelligence (MI) construct, provides such a new angle on many areas of the behavioral sciences. The cognitive mating mechanisms of MI include both species-typical and individual-differences features. While evolutionary psychology has tended to focus mainly on behavioral displays of physical qualities such as strength, virility, and athleticism, the MI construct focuses on psychological qualities (mental fitness indicators) such as confidence, kindness, creativity, intelligence, resourcefulness, status, humor, and mental health. Awareness of MI in the larger society should increase our appreciation of psychological and mental qualities in a potential mate in addition to purely physical qualities. Further, sex education in the schools can be improved by being informed by the MI framework. MI construct can allow us to come toward a more complete understanding of human intelligence.

After many years of inconclusive findings in the well-researched field of sex differences in general intelligence, Lynn (1994) made a novel contribution by proposing a developmental theory to explain differences in mean performance on measures of general intelligence. The theory posits that due to differing maturational rates, females outperform males prior to 15. years of age, while males outperform females from 15. years of age onwards through adulthood. The Raven's Progressive Matrices are often used in such investigations of group differences as they are considered to be among the best measures of general intelligence. To date, inconsistent results have been reported and may be attributed to the non-representative nature of the data samples and the use of statistical measures that fail to identify test item bias or the reliable evaluation of group differences. Using a nationally representative sample of children, multiple-group confirmatory factor analyses have been used to assess mean differences in younger (7-14. years) and older (15-18. years) groups. No significant differences were found in mean performance or score variance, failing to provide evidence for a Developmental Theory of Sex Differences in general intelligence. © 2011 Elsevier Ltd.

The author's theory that among adults men have a higher mean IQ than women has been critized by Mackintosh. His criticisms are examined and found wanting. New evidence is adduced that men obtain higher means than women on Raven's Progressive Matrices.

Our analysis of Medical College Admission Test subtest scores by writing hand preference and sex suggests that (a) right hemispheric dominance is associated with intellectual giftedness in verbal reasoning (left-handers obtained higher scores on the verbal reasoning test and were overrepresented in the upper tail of the distribution), (b) different patterns of brain lateralization are associated with different subcomponents of cognition (right-handers scored higher, on average, on the writing test and were overrepresented in the upper tail of the distribution), and (c) men generally score higher than women on tests of scientific knowledge (the most striking differences between men and women were on the biological and physical science tests).

Of all the controversial issues surrounding IQ tests, few have generated more heat and less light than the question whether different groups in our society differ in average IQ. Those who study, and find evidence of, such differences believe that they are addressing a legitimate scientific issue and one whose implications, however unpalatable they may be, society ignores at its peril. Their critics insist that the question has no intrinsic scientific interest whatsoever, and conclude that those who study it are either naive, deceiving themselves or only too happy to find justification for their own comfortable position within an unjust and unequal society. In the case of sex differences in IQ scores, at least, one could argue that both sides have got it largely wrong. With one exception, there is relatively little social or political implication in such differences as there are. More importantly, however, arguments will be presented against the critics' view that such research is of no intrinsic scientific interest. On the contrary, it has already helped to answer some important scientific questions about the nature of IQ, and has the potential to answer more. Unfortunately, those who engage in such research have usually failed to see this.