Guest post by Dr. Michael Daly
I started my research for this piece using the lesser known research tool; Google auto-complete. Into the sacred search engine I typed ‘women are more’, pressed spacebar and took a deep breath as the top searches were unveiled. Luckily these were highly relevant to this piece: number one was ‘women are more emotional than men’ followed by ‘women are more intelligent than men’. Then I tried ‘men are more’ and Google told me the most common searches are ‘men are more intelligent than women’ followed by ‘men are more romantic than women’.
This tells me a number of things. Firstly, both men and women seem to care about who is more intelligent, in fact it appears to be the main point of contention between the sexes. Secondly, there are a lot of closet romantics out there. Resisting the temptation to focus the rest of this piece on why some men need confirmation from Google that they can be romantic too, I will progress to the scientific literature on gender differences in intelligence.
Traditional approaches to examining gender differences in intelligence have often been to give men and women an intelligence test and to see who does better. For instance, Paul Irwing and Richard Lynn produced a meta-analysis which came to the conclusion that men have an IQ 4.6 points higher than women. By re-examining this paper and doing sensible things like considering that some studies have many more participants than others and should be weighted appropriately, Blinkhorn concluded that men show a slight advantage (1.5 IQ points). Last year, Flynn and Rossi-Case examined test scores from five advanced nations and found no sex differences in performance on the same test studied by Irwing and Lynn.
One area where it has been suggested that males have a substantial biologically based advantage is in spatial intelligence. This encompasses abilities like mentally rotating objects and judging spatial relations with respect to the orientation of one’s body. In a recent study, Hoffman and colleagues question this advantage, and ask whether it is genetically determined or emerges from how males and females are raised in different societies. They ingeniously examine two genetically similar tribes from Northeast India, the patrilineal Karbi tribe and the matrilineal Khasi tribe. They find that when men and women are raised in a society where females dominate there are few gender differences in performance on a spatial test. In the male dominated society the typical male advantage emerges.
This creative approach to examining gender differences in intelligence was hampered somewhat by substandard measurement of spatial intelligence. However, it does provide an insight into how research into gender differences in intelligence can move beyond merely documenting differences between men and women. For instance, experimental research has shown that when female students are asked to think of themselves positively (e.g. as a student from a selective college) they perform close to the levels of male students on a test of spatial intelligence. When female students are reminded of their gender the sex difference in spatial intelligence widens.
It seems possible to conclude that the most recent evidence shows that the intelligence levels of men and women differ little on average. Where gaps are present on intelligence subtests like spatial abilities these appear to be due, at least in part, to socialization processes and the effects of gender stereotypes.
One contentious point remains, which is the finding that men show more variability in intelligence than women. This means that on average men and women may not differ in their intelligence, but there may be more men with extremely low and high IQ’s than there are women. A proponent of this idea, Dr. Helena Cronin from London School of Economics, suggests that this means you’ll find “more dumbbells but more Nobels” amongst men. However, this idea too has been recently contested with emerging findings from the British Millenium Cohort Study of over 18,000 children showing that 5 year-old girls are overrepresented in the top 10% of intelligence levels. Although we know that girls typically show an IQ advantage over boys until the teenage years, this study is novel in that it shows that girls dominate the ‘outlier’ portion of high intelligence scores.
The future of intelligence research is likely to move beyond simply examining gender differences at a single time-point in a given society. New research will examine sex differences in intelligence in societies which differ in their socialization practices, will track changes over time, and will use experimental techniques to show the effects of gender stereotypes on intelligence test performance. In this way scientific research will undoubtedly lead to a clearer picture of the foundations of gender differences and similarities in intelligence.
Michael Daly is a lecturer and researcher in Behavioural Science and Public Health.
Some key references:
Flynn, J. R., & Rossi-Case, L. (2011). Modern women match men on Raven’s Progressive Matrices. Personality and Individual Differences, 50, 799–803. DOI: 10.1016/j.paid.2010.12.035
Hoffman, M., Gneezy, U., & List, J.A. (2011). Nurture affects gender differences in spatial abilities. Proceedings of the National Academy of Sciences USA, 108, 14786–14788. DOI: 10.1073/pnas.1015182108
Irwing, P., & Lynn, R. (2005). Sex differences in means and variability on the Progressive Matrices in university students: A metaanalysis. British Journal of Psychology, 96, 505−524. DOI: 10.1348/000712605X53542