Learning to read is a struggle for millions of kids, either because of learning disabilities or because they simply haven't had enough exposure to spoken language. But the hard part isn't helping those kids learn to read—that, it turns out, researchers seem to have a good handle on. The trick is finding the kids who need help well before reading becomes a problem. Now, researchers have created a test that could identify at-risk kids as young as four years old: put them in a noisy place, and see how well their brains process consonants.

"Learning to read is a chief developmental milestone with lifelong consequences," write Travis White-Schwoch, Nina Kraus, and colleagues at Northwestern University's Auditory Neuroscience Lab today in PLoS Biology. "[A]lthough there are effective interventions for struggling readers, an ongoing challenge has been to identify candidates for intervention at a young-enough age."

What's more, tests in three- and four-year-olds showed the same brain responses accurately predicted how those kids would perform on literacy tests taken a year later.

One clue, the Northwestern team notes, lies in the connection between literacy and the way the brain processes language early in life. Previous studies have found, for example, that struggling readers have a particularly difficult time making out words and individual syllables in noisy environments—a playground, say, or a kindergarten classroom. That suggests that how well kids process speech in noisy places could predict whether they'll struggle with reading well before any difficulties arise.

White-Schwoch, Kraus, and the rest of the team tested that idea by sitting 37 four-year-olds down in separate booths to watch a movie of their choice while also piping in the sounds of six people babbling—"speaking semantically anomalous English sentences," as the team puts it—into earphones placed in the kids' right ears. In the same ear, the team played audio of a single person repeating the syllable "da" over and over. (Kids could hear the movie through their left ears.) All the while, the researchers monitored electrical activity in the kids' brains using an electroencephalogram to see how quickly and consistently their brains responded to the "da" sounds.

Those brain signals, it turned out, could be used to predict kids' scores on a second test of phonological awareness, the extent to which a child understands the sounds that make up words and sentences, and an important indicator of early language ability. In fact, the researchers were able to build a model that predicted those scores to within about two points on average, or roughly 10 percent, after controlling for demographic factors such as age and sex. What's more, tests in three- and four-year-olds showed the same brain responses accurately predicted how those kids would perform on literacy tests taken a year later. In other words, a brain that can identify the "da" from the rest of the din was a brain that was ready to learn how to read.

"[O]ur view is that by establishing these brain-behavior links in preschool children, our findings can pave the way for auditory-neurophysiological assessment in [children younger than four], in addition to children who are difficult to test using conventional means," the team writes.

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