Although people with the reading and language disorder known as dyslexia exhibit a common disruption of brain activity, their performance on reading tests varies greatly from one country to another, according to a report in the March 16 Science.
There’s a simple reason why individuals with dyslexia read better in certain countries, according to neuroscientist Eraldo Paulesu of the University of Milan Bicocca in Italy and his coworkers. Those who read languages such as Italian–in which specific letter combinations almost always stand for the same sounds–have the advantage over those who read languages with less-consistent spelling rules.
In English and French, for example, the same letters often have several associated sounds (as in mint and pint or cent and cat in English) or different letters for the same sounds (as in au temps and autant in French). For dyslexics, such languages are obstacle courses of spelling irregularities.
In another part of their study, Paulesu and his coworkers used positron emission tomography scanners to measure blood-flow changes in the brains of 72 adults as they read real and nonsense words in their native languages. Equal numbers of volunteers came from England, France, and Italy. Half from each country had dyslexia.
All dyslexic readers exhibited the same pattern of reduced left-brain activity, as indicated by drops in blood flow in that part of the brain. Despite this evidence for a common neurological flaw in dyslexia, however, those from Italy scored much higher than their European counterparts on a reading test.