The language barrier
Why do Italians with dyslexia have an inbuilt advantage compared with English children? Usha Goswami explains
Does dyslexia really exist? Of course. All over the world, it is recognised as a specific learning difficulty intimately linked to the way we process language. Recent scientific research has found that dyslexia reflects atypical development in learning the sound structure of language its "phonology".
Modern brain imaging helps to show where problems may lie. In skilled readers, brain activity in the left hemisphere's network of spoken language areas increases as they read. In children with developmental dyslexia, this network activity is reduced and there is more activity in right hemisphere networks.
Particularly crucial is an area in the left hemisphere that turns print into sound. It is called the posterior superior temporal cortex. All children with dyslexia find it difficult to count syllables in spoken words, to judge whether spoken words rhyme and to retain speech-based information in short term memory.
The neural inefficiencies which result in dyslexia are shared across languages, with a similar prevalence of 5 to 7 per cent. Dyslexics in Chinese, French and Italian show similar characteristics. Nevertheless, its manifestation differs according to language. This is because of syllable structure and spelling systems.
Children with dyslexia learning to read languages such as Italian and Greek are best off developmentally. Syllable structure is simple: mostly consonant vowel pairings, as in mama. There is a consistent, one-to-one correspondence between letters and sounds. In these languages, dyslexics show slow, effortful but accurate reading and poor spelling.
Children with dyslexia find it more difficult learning to read in languages such as English. The syllable structure is complex. Correspondence between letters and sounds is inconsistent (for instance, "a" makes a different sound in make, man, mark and mall). English dyslexic children show inaccurate reading, slow decoding and poor spelling characteristic of dyslexia in other languages.
Studies in psychology and neuroscience reveal important new information about how the brain builds a language system. Before they produce words, infants learn the basic sounds (called "phonemes"), the order they occur, and how to segment the stream of sound into separate words and syllables. Segmentation depends on speech rhythm and stress (called "prosody").
Babies between one and four days old can distinguish between languages such as Dutch and Japanese using rhythmic cues. This is a basic mammal skill: research has shown that rats and monkeys can also distinguish Dutch from Japanese. Early babbling also reflects rhythmic differences between languages. Adults who are played taped babble from French, Cantonese and Arabic infants can distinguish each "language".
Apes babble too, producing calls with tonal notes, repetition, rhythm and phrasing. Rhythmic structure is basic to how the mammals' brains process and produce sounds (infants babble syllables, not phonemes).
In humans, the way carers speak to babies is important. This "motherese" (although fathers do it, too) uses higher pitch and increased syllable length for emphasis.
Cognitive neuroscience has shown there are populations of neurons in the brain that oscillate at the syllabic rate of speech. These neurons align their intrinsic rhythmic activity to the start of each spoken syllable. Children with developmental dyslexia find it hard to tell when syllables start. Syllables with abrupt onsets, such as "ba", are more difficult to distinguish from those with extended onsets, such as "wa". This is true in a variety of languages including French, Hungarian and Finnish. Brain imaging studies also show this.
In languages with consistent spelling, children with dyslexia can use the written word to sharpen up their phonological system. In English, spelling is less helpful.
Structured teaching of how sound and spelling are linked is the best way to help. In English, this is challenging, because spelling-sound consistencies occur at two levels, rhyme and phoneme. One useful scheme that trains children to make the link at both levels is Sound Linkage.
Usha Goswami is Professor of Education and director of the Centre for Neuroscience in Education at the University of Cambridge.
1 Luo, H. amp; Poeppel, D. (2007). Phase patterns of neuronal responses reliably discriminate speech in human auditory cortex. Neuron, 54, 1001-1010.
2 Goswami, U. et al., (2002). Amplitude envelope onsets and developmental dyslexia: A new hypothesis. Proceedings of the National Academy of Sciences of the United States of America 99, 10911-10916. All our recent research papers are available via www.educ.cam.ac.uk
3 Goswami, U. (2005). Synthetic Phonics and Learning to Read: A Cross-Language Perspective. Educational Psychology in Practice, 21 (4), 273-282.
4 Sound Linkage is a research-based intervention programme, see www.york.ac.ukrescrl research.html