Does growing up with two languages really sharpen a child's cognition?

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To get past those limits, I used data collected from a large national study that followed 14,027 American children from kindergarten to fifth grade. They completed short cognitive tasks at nine time points along the way. I sorted them into four groups, one of which spoke only English at home. Two spoke Spanish at home: one group already knew English at school entry, while the other picked it up after starting school. The fourth spoke an Asian language alongside English, and throughout I accounted for family background, gender, and reading skills. All three bilingual groups gained working memory faster than their English-speaking peers and scored higher by fifth grade. On flexibility and on blocking out distraction, though, the groups ended up even. Two things I expected to matter did not. It made no difference when a child picked up the second language, or how similar the two languages were. The gap in working memory was also absent in the earliest grades and only appeared as children got older, so the benefit may need time and growing mental capacity to emerge. This study cannot prove cause and effect, and it reflects children growing up in the United States, where English is the majority language. Even so, the pattern is clear: bilingual experience seems to support one particular cognitive skill rather than cognition as a whole.

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