Science & Tech

Mounting case against notion that boys are born better at math

Elizabeth Spelke studies French testing data, finds no gender gap until instruction begins

Christy DeSmith

Harvard Staff Writer

July 3, 2025

6 min read

Elizabeth Spelke. Stephanie Mitchell/Harvard Staff Photographer

Twenty years ago, cognitive psychologist Elizabeth Spelke took a strong position in an ongoing public debate.

“There are no differences in overall intrinsic aptitude for science and mathematics among women and men,” the researcher declared.

A new paper in the journal Nature, written by Spelke and a team of European researchers, provides what she called “an even stronger basis for that argument.”

A French government testing initiative launched in 2018 provided data on the math skills of more than 2.5 million schoolchildren over five years. Analyses showed virtually no gender differences at the start of first grade, when students begin formal math education. However, a gap favoring boys opened after just four months — and kept growing through higher grades.

The results support previous research findings based on far smaller sample sizes in the U.S. “The headline conclusion is that the gender gap emerges when systematic instruction in mathematics begins,” summarized Spelke, the Marshall L. Berkman Professor of Psychology.

Back in 2005, her position was informed by decades of work studying sensitivity to numbers and geometry in the youngest members of human society.

“My argument was, ‘OK, if there really were biological differences, maybe we would see them in the infancy period,’” recalled Spelke, who laid out her evidence in a critical review for the journal American Psychologist that year.

“We were always reporting on the gender composition of our studies, as well as the relative performance of boys and girls,” Spelke continued. “But we were never finding any differences favoring either gender over the other.”

“The fact that there are no differences in infants could be because the abilities that show gender effects actually emerge during preschool.”

The possibility remained that differences in skill or even motivation surface later in the lifecycle.

“The fact that there are no differences in infants could be because the abilities that show gender effects actually emerge during preschool,” Spelke said.

Recent years have found the psychologist applying her research on early counting and numeral-recognition skills via educational interventions, all analyzed and refined through randomized control experiments.

One of the world’s most influential researchers on early learning, Spelke recently partnered with Esther Duflo, an MIT economics professor and Nobel laureate, to advise the Delhi office of the nonprofit Abdul Latif Jameel Poverty Action Lab (J-PAL). The group is working with the governments of four separate Indian states to develop and test math curricula for preschoolers, kindergartners, and first-graders.

Alongside her longtime collaborator, the cognitive neuroscientist Stanislas Dehaene, Spelke also serves as an adviser on the French Ministry of Education’s Scientific Council. The nationwide EvalAide language and math assessment was introduced with the council’s help in 2018. The project’s goal, Spelke explained, is establishing a baseline measure of every French child’s grasp of basic numeracy and literacy skills, while supporting the ministry in its commitment to implementing an evidence-based education for all French schoolchildren.

Spelke co-authored the Nature paper with Dehaene and eight other researchers, all based in France. Specifically analyzed were four consecutive cohorts of mostly 5- and 6-year-olds entering school between 2018 and 2021.

As in many countries, French girls tested slightly ahead of French boys on language as they started first grade in the fall. But the gender gap was close to null when it came to math.

“That definitely connects to the earlier issue of whether there’s a biological basis for these differences,” Spelke argued.

French first-graders were then reassessed after four months of school, when a small but significant math gap had emerged favoring boys. The effect quadrupled by the beginning of second grade, when schoolchildren were tested yet again.

“It was even bigger in fourth grade,” said Spelke, noting that French children are now assessed at the start of even-number grades. “And in sixth grade it was bigger still.”

For comparison, EvalAide results show the literacy gender gap was reduced by the first year’s four-month mark and changed far less as students progressed to higher grade levels.

Why would a gender gap widen on math specifically as students accumulated more time in school? According to Spelke, the paper provides “only negative answers” concerning ideas about innate sex differences and social bias.

“If there was really a pervasive social bias, and the parents were susceptible to it,” she said, “we would expect boys to be more oriented toward spatial and numerical tasks when they first got to school.”

Delving further into the data yielded more results that caught the researchers’ interest. For starters, Spelke’s co-authors could disaggregate the findings by month of birth, with the oldest French first-graders turning 7 in January — nearly a year before their youngest classmates. The math gap was found to correlate not with age, but with the number of months spent in school.

Another noteworthy result concerned the COVID-19 pandemic, which wiped out the last 2.5 months of first grade for children who enrolled in fall 2019. “With less time in school, the amount of the gender gap grew by less than it did in the other years where there wasn’t a long school closure,” Spelke said.

The 2019 cohort yielded one more striking result. Earlier that year, French schoolkids had placed at the very bottom of 23 European countries on the quadrennial Trends in International Mathematics and Science Study. That sparked a national conversation: How could France, birthplace of the great René Descartes, be trailing its peers in mathematics?

In May 2019, the French Education Ministry, with the support of its Scientific Council, called for the introduction of more math curriculum during kindergarten. For the first time, an ever-so-slight gender math gap appeared that fall for those entering first grade. It hadn’t been there in 2018 but remained detectable in results from the 2020 and 2021 cohorts.

The overall results, the most conclusive to date, suggest it’s time to shelve explanations based on biology or bias. Instead, it appears there’s something about early math instruction that produces gender disparities.

“We still don’t know what that is exactly,” said Spelke, who plans to spend much of her 2025-26 sabbatical year in France. “But now we have a chance to find out by randomized evaluations of changes to the curriculum.”