For psychologists, there’s no question that human cognition — the way we process information — has dramatically improved over the last century thanks to improvements in nutrition, health care, sanitation, and social equality. But what if improvements in society over time — the same kinds of improvements that increase life expectancies and lower infant mortality rates — benefitted about half the population more than it did the other? Those are the findings of a new study, published today in Proceedings of the National Academy of Sciences, which stipulates that women’s cognitive abilities benefit far more from improvements in social conditions than men's do. And, in some cases, women surpass men altogether.
women’s cognitive abilities benefit far more
"As living conditions increase, so do men and women’s cognitive abilities — but women’s more than men’s," says Agneta Herlitz, co-author of the study and a psychologist at the Karolinska Institute in Sweden. Other studies have been able to show increases in cognition over time, Herlitz says, "but we show that this happens more for women than for men, and that gives rise to slightly different patterns in cognitive differences."
Herlitz and her colleagues used cognitive data from 30,000 individuals that had been gathered in 2006 across 13 European countries. The data set included people born between 1923 and 1957. This information allowed them to analyze the participants’ cognitive abilities with regards to numeracy, episodic memory — their ability to recall moments — and category fluency, or the ability to name as many objects, animals, or plants as possible within a certain category. Then, they compared these results to total fertility rate, infant mortality rates, educational levels, life expectancy rates, and gross domestic product (GDP) that each participant experienced at the age of 25. The researchers did not include medical information in their analysis, however.
"a slight advantage in episodic memory."
"Our result show that women in these European countries have a slight advantage in episodic memory," Herlitz explains. They also found that improving social conditions eliminated differences in category fluency between men and women.
"We don’t know why" women excelled more than men in these tasks when social conditions improved, Herlitz says, but researchers think it might have to do with the fact that women, generally, are "treated more badly," so they "start from a lower level," and may subsequently get a bigger boost from improvements that also benefit men.
That wasn’t the case across the board, Herlitz point outs. "It’s not always that [women] are better than men, because they are still much worse in the numeracy task." This, she says, might be because math proficiency tends to be encouraged in men more than in women. "The same can be said with verbal ability since people talk more to small girls." But separating biological components from cultural components is extremely difficult, she said. And "most researchers would probably say that there are biological differences at play here, as well as cultural and environmental factors."
"It’s not always that [women] are better than men."
Diane Halpern, former president of the American Psychology Association and an expert on sex differences in cognition, agreed with Herlitz in an email to The Verge. "The development of cognitive abilities is always both" a matter of nature and nurture, she said. "It is more usual to think about the multiple ways biology, individual differences, societal, and cultural factors interact."
This might explain why Herlitz and her team used the word "gender," a social construct, in the study, without separating it from the biological term "sex." "I have used sex differences and gender differences in the past without much thought," Herlitz says.
Still, some cognition experts favor environmental factors over biological ones, as evidenced by David Reilly, a psychologist at Griffith University in Australia, who told The Verge that "if there were strong and immutable biological differences, we wouldn't see this shift in abilities over time, or across regions."
Reilly also pointed out how unique Herlitz’s study is, because it found an association between gender equality and cognitive abilities in older adults. "We don't have any studies linking older adults ability to gender equality measures," he said in an email. But "what [the researchers] have done is find a link between gender equality and cognitive ability in previous generations," which means they’re long-lasting. "That's very impressive," he said, "and has some important public policy and education implications."
Yet, Janet Hyde, a psychologist the University of Wisconsin-Madison who did not participate in the study, isn’t convinced by some aspects of the research. She told The Verge that although she thinks the findings make sense, comparing people born before 1945 with people born afterward is questionable, especially when that information does not include medical histories. "They have birth cohorts from as early as 1927," she said in an email. "Those birth cohorts lived through WWII, during major periods of starvation as well as exposure to bombing and other events that would be likely to lead to PTSD." All of those events would have effects on cognitive function in later life, so it’s hard to make "meaningful comparisons of groups who experienced that major event with those born after it."
But Halpern doesn't think this is a problem, because the researchers used a very large sample size and selected each participant at random — a method that allowed them to treat the health of their sample as approximately equivalent. "A major event like WWII is obviously important," she said, but "there are always issues in comparing cross-sectional age groups." That shouldn’t change the conclusions, she said. "The paper is very well done," and "the science is sound."
"For some reason, it’s hard to accept that there may be differences in men and women."
Both Halpern and Herlitz know this study will raise many questions, and might even be deemed controversial. But raising questions is "what a good research paper should do," Halpern says. And for Herlitz, the controversy that this study, and others, might generate is misguided. "For some reason, it's hard to accept that there may be differences in men and women," Herlitz explains, adding that gender differences do not in any way need to imply that we should not live in gender-equal societies. And in truth, she says, it's not these differences that cause problems, but how we value them. "Obviously the abilities that women have are valued less — that's what affects things."