When the results came from the international study on reading and mathematics (PISA), it seemed to confirm the old stereotype that boys perform better than girls in math. In the US, girls performed about 10 points below the boys. However, in some countries, such as Sweden, there was no statistical difference, and in Iceland, girls actually outperformed boys. But the PISA study could not inform about the reasons for these differences.

One clue came in a study led by Paolo Sapienza, published in Science. She looked at the PISA results in math from 276.000 children in 41 countries and compared it to an index of equality, called the Gender Gap Index (GGI) from the World Economic Forum. This index is a single number from 0 to 1, based on factors such as the proportion of women who work, or are involved in politics. It turned out that the gender differences in math were directly related to the GGI: countries with the largest GGI had also the largest advantages for boys. When the researchers statistically corrected for the GGI, there was no longer any differences in math between boys and girls.

This is all very interesting (although a bit depressing for US girls), but the question is: what are the mechanisms? One possible explanation comes from a study of how men and women are affected by math anxiety. When participants were told that they were about to perform a working memory task (which included math operations as a kind of distractor) to get norms for student, men and women performed equally. But when the same test was given with the information that this was a test of complex mathematics in order to compare males and females, performance in female participants dropped almost 30 percent.

The experiment was repeated, now with both working memory and math tests. Again, the females who were informed that they were going to take a math test performed worse, on both math and working memory tests. The researchers could also show that the stress was most closely associated to impairments in working memory, and it was the impaired working memory which caused the lower math performance.

The link between working memory and math is well established (see my previous blog post). Stress is one of the most powerful factors that cause the working memory capacity to go up and down from one moment to the next. The explanation can be found in how stress related substances effects neurons in the prefrontal cortex, with consequences for academic performance. Hopefully, information to both parents and girls about these mechanisms could in itself be helpful in preventing math anxiety.

In my recent book: "The Learning Brain - Memory and Brain development in Children" I write more about the effects of stress on working memory, including the effects of chronic stress.

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