Gender Difference and Intelligence: Is There Any Correlation?
Among researchers around the world, it has been quite an intriguing aspect whether gender difference has any correlation with intelligence. They have made investigations on the differences in the distributions of cognitive ability test scores between males and females to arrive at any possible correlation between sex and intelligence.
MORE MEN AT THE LOWEST AND THE HIGHEST LEVELS
The researchers have relied upon parameters pertaining to the differences in IQ level as well as individual skills components. In IQ tests, psychometricians rely upon a variety of skill factors to arrive at the measure of ‘g’. The G factor is a hypothesized general factor of intelligence. These analyses have revealed that differences between men and women's median scores are minimal or even negligible. However, men have an increasing over-representation at the extreme levels. That is, men appear in an increasing number both at the lowest and the highest levels of the scores in intelligence analysis parameters.
STUDIES IN THE 20TH CENTURY
About a century ago, as evidenced by Jackson and Rushton, the general consensus among the scientific community was that gender has no role in intelligence level. This view is supported by the work of Cyril Burt and Lewis Terman. By the close of the 20th century, it was the generally accepted finding that the differences in IQ between men and women are statistically insignificant. The studies of Hedges and Nowell stand testimony to this finding. As per the 1995 study of the American Psychological Association, there is no difference in average IQ between sexes.
However, some other studies carried out in the later half of the 1990s have revealed that the IQ levels of men and women differ a little. K. Warner Schaie in his book, ‘Developmental Influences on Adult Intelligence: The Seattle Longitudinal Study’, states that in spatial competencies there exist a few gender differences. In the "California Verbal Learning Test", data from 2,404 men and women were studied and it was so reported: "When mediating variables were controlled, gender differences tended to disappear on tests for which there was a male advantage and to magnify on tests for which there was a female advantage."
STUDIES IN THE EARLY 21ST CENTURY
In the early 21st century, a study by Richard Lynn from the analysis of a number of published tests including the standardized g-loaded Wechsler Adult Intelligence Scale-Revised revealed that the mean IQ of men is higher than that of women by about 3-4 points. In Lynn's meta-analysis conducted in 2004 it was revealed that the IQ of men in 5.0 points higher than that of women. In a study involving males and females aged 17 – 18 years conducted by Rushton also revealed that men had 3.63 IQ points higher than women. However, in another study it was found that women have 2-4 IQ points higher than men in later life. Again, a study conducted in 2009 men showed 3-5 IQ points higher than women.
In 2005, a study was conducted focusing on the ASVAB scores of 1,292 pairs of opposite sex siblings. It was under the leadership of Ian Deary, Paul Irwing, Geoff Der, and Timothy Bates that the study was conducted. It showed a remarkable trend among the intelligence scores of each gender in relation with the other. The study revealed the number of males double the number of females in the top and bottom 2% of scores. That is, the study demonstrated a significant variance in the score of males. The study also revealed a very small average male advantage in G (factor).
THE HISTORICAL PERSPECTIVE
In its historical perspective, the correlation between gender and intelligence has passed through different phases. When universal adult suffrage was a political and social issue in some regions of the world during the nineteenth century, gender and intelligence was taken as a topic of study. It was proposed by many as a prerequisite for the granting of suffrage that men and women should be at the same level of intelligence. Researchers such as Leta Hollingworth are of the view that the potential of women was not allowed to grow as women were confined to domestic chores and child-bearing. For the purpose of employment, from late twentieth century, sex differences in intelligence have been a matter of study to determine the proportionate payment for women in relation to their skill and intelligence.
(1) Sex differences in latent cognitive abilities ages 6 to 59: Evidence from the Woodcock–Johnson III tests of cognitive abilities http://www.iapsych.com/articles/keith2008ip.pdf
(3) Intelligence: Is there a sex difference in IQ scores? http://www.nature.com/nature/journal/v442/n7098/full/nature04966.html
(5) Colom, R.; García, L.F.; Juan-Espinosa, M.; Abad, F. (2002). "Null Sex Differences in General Intelligence: Evidence from the WAIS-III" (PDF). Spanish Journal of Psychology 5 (1): 29–35. PMID 12025362. http://www.ucm.es/info/Psi/docs/journal/v5_n1_2002/art29.pdf
(8) Intelligence: A gender bender http://www.nature.com/nature/journal/v438/n7064/full/438031a.html
(10) Males have greater g http://psychology.uwo.ca/faculty/rushtonpdfs/2006%20intell%20jackson%20&%20rushton.pdf