THAT men and women think differently is now widely accepted. Why they do so is another matter. One possible explanation is that it is an evolutionary trait. In the time of hunting and gathering different skills were required: men needed to spend time away from camp, tracking animals and fighting off intruders, and women needed social skills to bring up children. Yet there are bound to be many other factors at work for this variation to survive into modern times. The latest research suggests that living standards and access to education probably bear more responsibility for cognitive disparity between men and women than genes, nursery colours or the ability to catch a ball.

Previous studies have shown that male and female brains are wired differently. A study last year by Ragini Verma of the University of Pennsylvania used sophisticated imaging techniques to show variations in dominant connections in the cerebrum, the part of the brain that does the thinking, between men and women. Dr Verma speculated that these wiring changes help to explain why women tend to have better memories, social adeptness and an improved ability to multitask.

Now Daniela Weber of the Wittgenstein Centre for Demography and Global Human Capital in Vienna, and her colleagues in Austria and Sweden, have used a large sample of people to suggest why such changes come about and, importantly, how the differences can change. The group's analysis, reported this week in Proceedings of the National Academy of Sciences, finds that the cognitive performance of women—much more so than men—benefits from factors such as greater employment opportunities, increased economic prosperity and better health.

Ms Weber and her colleagues based their work on interviews with 17,000 men and 14,000 women carried out by an initiative called the Survey of Health, Ageing and Retirement in Europe, conducted in 2006-07. The interviewees, aged 50 to 84, lived in 13 European countries and were subjected to three tests for cognitive performance. They were grouped into three regions: Northern Europe (Denmark and Sweden), central Europe (Austria, Belgium, the Czech Republic, France, Germany, the Netherlands, Poland and Switzerland) and southern Europe (Greece, Italy and Spain).

For each country a regional development index (RDI) was adopted: an amalgam of GDP, family size, infant mortality, life expectancy and national education levels. These criteria were selected as a representation of a country's educational and living standards for the birth years of the interviewees, and then compared with their cognitive performance.

A case of misremembering

That performance was determined using tests for episodic memory (the retention of words in memory), category fluency (naming examples of, say, animals) and numeracy. Women are expected to outperform men in episodic memory and men generally do better in numeracy. Neither sex is thought dominant in category fluency.

Episodic memory is important as it is linked to emotion; the brain remembers unconnected words by linking them to a memory or imagined situation. It is the emotion of the memory that supposedly helps the brain remember the word. Whether women actually are more empathetic than men, or if society has expected such capacity from the principal child-carers for so long that it has become ingrained, is debatable. The same goes for numeracy. Is science dominated by men because they are better at it, or because it was a career choice not widely open to women before the late 20th century?

The new study does not seek to answer these questions. But it pushes research further towards answers. As expected, in episodic-memory tests women outperformed or were equal to men in every geographic area and across almost all age groups. The results for the numeracy tests were even starker. Men outperformed women in all geographical areas and in all age groups. The differences in category fluency were so slight as to be statistically irrelevant. But the really startling discovery was how the results changed over time and by region.

The results showed that as countries improved in RDI terms, the cognitive performance of the whole population was raised. Northern Europe rated highest across all age groups, followed by central and then southern Europe. Unexpectedly, the study also showed that the better-developed a country, the higher the rate of increase in women's cognitive abilities. Quite why women benefit disproportionately from societal improvements is not known. It may be that they are starting from a more disadvantaged level.

Whatever the reason, this study suggests that cognitive differences between men and women are not solely inherited. It suggests that, to a degree hitherto unacknowledged, they are learned from the roles a society expects males and females to perform, and that those differences can change as society changes. Modern times require modern thinking.