Former guerrillas in Colombia have helped neuroscientists locate which parts of the brain are involved in literacy. This major finding can help explain why we can sometimes finish the sentences of others.
The study, funded by the Wellcome Trust and the Spanish Ministry of Education and Science, has enabled the study's researchers to see how brain structure changed after learning to read.
Researchers believe the reason that dyslexics struggle to read at speed is that they are missing the ability of the human brain having a built in predictive text function like those on a mobile telephone.
The neuroscientists found that the reason most people can predict words and sentences as they are being scanned by the eye.
Rather than read every word and sentence to the end before coming up with its meaning, the brain makes an educated guess and then moves on.
As people become more literate, the brain becomes ever more adept at predicting sentences and therefore quicker at reading.
The research has been published in Nature.
"Separating out changes in our brains caused by learning to read has so far proven almost impossible because of other confounding factors," explains Professor Cathy Price, a Wellcome Trust Senior Research Fellow at UCL (University College London).
"Working with the former Colombia guerrillas has provided a unique opportunity to see how the brain develops when reading skills are acquired," the expert added.
In the study, researchers examined magnetic resonance imaging (MRI) scans of the brains of twenty guerrillas who had completed a literacy programme in their native tongue (Spanish) in adulthood. They compared these to scans of twenty-two similar adults prior to commencing the same literacy programme. The results revealed which brain areas are special for reading, prompting new research in the UK on how these regions are connected in adults who learn to read in childhood.
The researchers found that for those participants who had learnt to read, the density of grey matter was higher in several areas of the left hemisphere of the brain. As might be expected, these were the areas that are responsible for recognising letter shapes and translating the letters into speech sounds and their meanings. Reading also increased the strength of the 'white matter' connections between the different processing regions.
Particularly important were the connections to and from an area of the brain known as the angular gyrus. Scientists have known for over years that this brain region is important for reading, but the new research has shown that its role had been misunderstood.
Previously, it was thought that the angular gyrus recognised the shapes of words prior to finding their sounds and meanings. In fact, the researchers showed that the angular gyrus is not directly involved in translating visual words into their sounds and meanings. Instead, it supports this process by providing predictions of what the brain is expecting to see.
"The traditional view has been that the angular gyrus acts as a 'dictionary' that translates the letters of a word into a meaning," explains Professor Price.
"In fact, we have shown that its role is more in anticipating what our eye will see - more akin to the predictive texting function on a mobile phone," the expert added.