The extreme man
Men are more extreme than women. According to the doctoral dissertation of biostatistician Anne-Catherine Lehre there are more men among the lightest and heaviest, tallest and shortest, those who fail exams and those who get the top marks.
Photo: Colourbox.no
Wider variability in birth weights
In her doctoral dissertation "Sex matters: Looking into variability. The variability hypothesis, the 2003 Quality Reform in higher education in Norway, and the role of BGT1 in seizure control" Anne-Catherine Lehre and colleagues have studied the differences in the variability of a range of characteristics in men and women.
By studying approximately 48,000 birth weights of babies born in Norway in 2002, they found that new-born baby boys exhibited wider variability in birth weights at term.
- This means that there are relatively more boys of low and high weight compared with the girls, Lehre says.
According to her, this is a very interesting discovery.
- Even if we see similar differences between the sexes in the variability of weight at an adult age, with men being overrepresented among those of lowest weight and highest weight, analyses of birth weight show that biology contributes to the boys being overrepresented at the extremes even before cultural and societal factors become apparent.
Quality reform in women's favour
Lehre's research work has also resulted in findings that indicate that men's exam marks are more variable than women's. Women have a tendency to congregate around the average, and there are relatively more women than men with average marks.
Anne-Catherine Lehre.
Photo: Gunnar F. Lothe, UiO.
- In order to test whether changes in the environment affect the sexes differently, we analysed men's and women's exam marks before and after the Quality Reform in higher education in Norway in 2003. This reform changed teaching, learning and assessment methods so greatly that it can be viewed as a change in the student environment, says Lehre.
The results from the analysis showed that the changes in teaching and assessment methods favoured women. Women are getting higher average marks than men after the reform. Nevertheless there are more men than women, both before and after the reform, who are getting top marks or failing. This indicates that changes in the environment can affect the average values of the sexes differently, but that men's marks continue to be more extreme.
- When we take into account the students' ages, native municipalities, specialised studies and types of higher education, we get the same result regarding genders, explains Lehre.
In total, almost 6.5 million exam results from Norwegian universities and university colleges in the period 1990-2007 have been analysed.
Why do men vary more than women?
There are several different theories as to why men are more variable than women.
An interesting theory, according to Lehre, is the importance of the X chromosome. Women have two X chromosomes, while men have an X chromosome and a Y chromosome. As men have only one X chromosome, the genes on the X chromosome are fully expressed. For women on the other hand you can say, in a simplified way, that one X chromosome is expressed in half of the cells, and the other X chromosome is expressed in the other half of the cells.
- The theory asserts that women are thereby an average of their two X chromosomes, and that there are therefore fewer extreme women, says Lehre.