Girls in Science (Gender Differences)

This is a sequel to a previous post in this blog, "Girls in Science". That previous post was based on an article from the blog of The Guardian. This week, a new article has been published in the open journal PLOS One. "Sex Differences in Mathematics and Reading Achievement Are Inversely Related: Within- and Across-Nation Assessment of 10 Years of PISA Data", by Stoet and Geary, examines closely not just the scores in mathematics but also in reading for millions of students across seventy five countries to decipher gender differences:

Abstract 

We analyzed one decade of data collected by the Programme for International Student Assessment (PISA), including the mathematics and reading performance of nearly 1.5 million 15 year olds in 75 countries. Across nations, boys scored higher than girls in mathematics, but lower than girls in reading. The sex difference in reading was three times as large as in mathematics. There was considerable variation in the extent of the sex differences between nations. There are countries without a sex difference in mathematics performance, and in some countries girls scored higher than boys. Boys scored lower in reading in all nations in all four PISA assessments (2000, 2003, 2006, 2009). Contrary to several previous studies, we found no evidence that the sex differences were related to nations’ gender equality indicators. Further, paradoxically, sex differences in mathematics were consistently and strongly inversely correlated with sex differences in reading: Countries with a smaller sex difference in mathematics had a larger sex difference in reading and vice versa. We demonstrate that this was not merely a between-nation, but also a within-nation effect. This effect is related to relative changes in these sex differences across the performance continuum: We did not find a sex difference in mathematics among the lowest performing students, but this is where the sex difference in reading was largest. In contrast, the sex difference in mathematics was largest among the higher performing students, and this is where the sex difference in reading was smallest. The implication is that if policy makers decide that changes in these sex differences are desired, different approaches will be needed to achieve this for reading and mathematics. Interventions that focus on high-achieving girls in mathematics and on low achieving boys in reading are likely to yield the strongest educational benefits.

There are interesting trends that this study has uncovered. First, although the post from The Guardian highlights the lower scores of girls from the United States in mathematics, this new study shows that for reading, there is an equally disturbing trend. Male students across the globe score lower in reading. Second, Stoet and Goery have demonstrated that in analyzing the scores, it is particularly useful to divide the data between high, average and low performers. Third, the absence of correlation between the gender differences in the exam scores and a country's set of gender equality indicators is especially striking.

The gender differences in mathematics and in reading as a function of student performance are indeed noteworthy:

Figure 1. Sex differences in mathematics (top) and reading performance (bottom).

Top: For each PISA assessment, the sex differences in mathematics (boys’ performance – girls’ performance) is displayed for the 5th, 50th, and 95th percentile of the performance distribution. Bottom: Similar for sex differences in reading (girls’ performance – boys’ performance).doi:10.1371/journal.pone.0057988.g001. Stoet G, Geary DC (2013) Sex Differences in Mathematics and Reading Achievement Are Inversely Related: Within- and Across-Nation Assessment of 10 Years of PISA Data. PLoS ONE 8(3): e57988. doi:10.1371/journal.pone.0057988

The figures above correspond to four different years of PISA tests. Clearly, the trend has not changed with time. Boys outperform girls in math while girls do better than boys in reading. These differences, however, depend on the type of students considered in the comparison. This is where an additional difference between math and reading lies. In mathematics, the gender disparity is much sharper among high performing students. Within students in the 95 percentile, the difference between boys' and girls' scores is about 20. The scoring here has been scaled so that a difference of 100 corresponds to one standard deviation. Keeping in mind that students usually choose majors in college in which they perceive themselves to be good at, Stoet and Goery also show the makeup of the percentiles in the math scores via the following table:

Table 1. Ratio of boys to girls in mathematics achievement at various percentiles.Stoet G, Geary DC (2013) Sex Differences in Mathematics and Reading Achievement Are Inversely Related: Within- and Across-Nation Assessment of 10 Years of PISA Data. PLoS ONE 8(3): e57988. doi:10.1371/journal.pone.0057988

With in the top 5% of students, there are roughly 2 boys per girl. This can perhaps partly explain why more male students are enrolling in science, technology, engineering and math fields. The corresponding table for reading is as follows:

Table 2. Ratio of boys to girls in reading achievement at various percentiles.Stoet G, Geary DC (2013) Sex Differences in Mathematics and Reading Achievement Are Inversely Related: Within- and Across-Nation Assessment of 10 Years of PISA Data. PLoS ONE 8(3): e57988. doi:10.1371/journal.pone.0057988

The reading disparity is more dramatic. Of course, this can be seen in the bigger differences shown in Figure 1. In the bottom 5%, in the most recent exam, a student is three to six times more likely to be male than female. These reading results are especially disturbing especially when one considers the fact that education across the globe is far from uniform. In these international exams, high performing students are usually from industrialized countries while developing countries usually comprise the lower brackets. Thus, the gender disparity in math is more evident in wealthy nations, while the gender disparity in reading is more evident in poor countries. This is doubly problematic. In poor countries, not only do most students (boys or girls) not do well in both math and reading, but boys score even lower in reading. The authors' explanation for this trend is: "... improvements in living conditions will benefit boys’ achievement across the continuum more than girls’ achievement, whereas deteriorating conditions will adversely affect boys more than girls." 

This is indeed a paradox. Oftentimes, gender equality in education is usually focused on increasing girls' access to quality education. The trends in the international reading exams indicate that in poor countries, the boys are actually the ones that need attention.