First author

Many believed that learning to read produces structural changes in the brain. Manuel Carreiras at the Basque Center on Cognition Brain and Language in Donostia–San Sebastián, Spain, wanted to explore the nature and extent of these changes. But most people learn to read as children, when a host of other neurological changes relating to development and early education are also occurring. Carreiras reasoned that the only way to get a glimpse of literacy-related brain changes in isolation would be to compare brain images of illiterate adults with those of people who had learned to read later in life (see page 983). He tells Nature how he managed to find enough volunteers.

How did you go about finding illiterate adults for the study?

It proved impossible to find a sufficient number of illiterate adults in Spain, so when Silvia Baquero, one of my graduate students, returned home to Bogota, Colombia, I asked her to look around. On her recommendation, we searched schools that work with illiterate pupils and found that in some schools, many of the students were former guerrilla fighters who had put down their weapons and were in the process of being reintroduced into society. Many had never had the chance to learn to read and were going through education programmes that would teach them.

How much do you know about the backgrounds of these individuals?

We don't know much about their backgrounds, or personal stories. But we did try to establish that they had no impediments to learning to read besides the fact that they had never been taught.

What did you compare?

Of the 42 adults we looked at, 22 were just about to enter into school programmes to teach them how to read and write. The others had already spent time in these programmes. We compared the brains of the two groups using magnetic resonance imaging.

What did you find?

That structural changes do occur in the mature brain during the acquisition of a skill such as reading. We found that the literate members of our group had more white matter in the splenium — a part of the corpus callosum, a structure that connects the brain's left and right hemispheres — than did the illiterate members. Then, in another population of literate adults who had learned to read as children, we used different imaging techniques to show that some of the same areas that had increased in those who learned to read as adults are connected structurally and functionally during reading.