Children growing up in low-income homes score lower than their wealthier peers on cognitive tests and other measures of scholastic success, study after study has found. Now mounting evidence suggests a way to mitigate this disadvantage: learning another language.

In an analysis published online in January in Child Development, Singapore Management University researchers probed demographic data and intellectual assessments from a subset of more than 18,000 kindergartners and first graders in the U.S. As expected, they found children from families with low socioeconomic status (based on factors such as household income and parents' occupation and education level) scored lower on cognitive tests. But within this group, kids whose families spoke a second language at home scored better than monolinguals.

Evidence for a “bilingual advantage”—the idea that speaking more than one language improves mental skills such as attention control or ability to switch between tasks—has been mixed. Most studies have had only a few dozen participants from mid- to high-socioeconomic-status backgrounds perform laboratory-based tasks.

Andree Hartanto, a doctoral candidate at Singapore Management University and the study's lead author, says he sought out a data set of thousands of children who were demographically representative of the U.S. population. It is the largest study to date on the bilingual advantage and captures more socioeconomic diversity than most others, Hartanto says. The analysis also includes a real-world measure of children's cognitive skills: teacher evaluations.

The use of such a sizable data set “constitutes a landmark approach” for language studies, says Jon Andoni Duñabeitia, a professor at Nebrija University in Madrid, who was not involved in the work. But Duñabeitia notes the data did not contain details such as when bilingual subjects learned each language or how often they spoke it. Without this information, Hartanto concedes, it is difficult to draw conclusions about how being bilingual could confer cognitive advantages.

Kenneth Paap, a psychologist at San Francisco State University, thinks other factors may explain higher performance in bilingual children. For example, they are more likely to be immigrants. Previous epidemiological studies have revealed a “healthy immigrant effect,” Paap says, referring to findings that immigrants on average have better physical health and lower mortality rates than native-born citizens. This benefit could extend to cognitive ability.

Hartanto agrees that it will take more work to untangle the complex relations among bilingualism, socioeconomic status and cognitive development. The new findings, he says, “show us that the answer to bilingual cognitive advantages should not be a simple yes or no.”