Even if you've never learned Italian, the pronunciation of the exclamation above can seem more instinctive than some of the quirkier words in the English language, such as 'sobriquet'. This is a characteristic of written languages as a whole: some, such as Italian, have a 'shallow' orthography — letters in the alphabet alone or in combination usually map uniquely to speech sounds. Others such as English are much more ambiguous (have a 'deep' orthography); for example, the 'o' in tomb, bomb or comb is pronounced differently in each word. These differences in the ease of reading for different languages have important implications for the study of dyslexia, as the variable nature and prevalence of this reading disorder across languages have led to doubts that it stems from a particular cognitive deficit. But now, by contrasting dyslexic and normal readers in languages with deep (English and French) and shallow (Italian) orthographies, a multinational group of researchers have provided strong evidence that dyslexia has a unitary neurocognitive basis.

The authors studied the differences in performance of reading and phonological tasks in English, French and Italian people with dyslexia and in normal controls matched for age and IQ. Tests were in the native language and included assessments of reaction time to words and non-words, digit-naming skill and auditory short-term memory for short and long words. The Italian dyslexic people performed consistently better when reading than their English and French counterparts, as might be expected given the shallower orthography of Italian. But crucially, despite the differences in performance across languages, the impairment in the performance of the dyslexic people relative to their controls was independent of language. Furthermore, positron-emission tomography studies of dyslexics and controls from the three countries revealed that reduced activation in the left-middle, inferior and superior temporal cortex and in the middle occipital gyrus was a feature common to dyslexia for word reading in all three language groups. So, as the authors conclude, it seems that “dyslexia has a universal basis in the brain and can be characterized by the same neurocognitive deficit”, with the effect of this deficit being less in languages with shallow orthography.