World Dyslexia Day
World Dyslexia Day brings attention to a specific learning difficulty that affects people in all languages. Dyslexia affects up to 700 million children and adults worldwide. Experiencing dyslexia has negative effects on self-esteem, education and mental health. New brain research suggests that the origins of dyslexia lie in atypical auditory processing of the speech stream, not in atypical visual processing of print, as previously believed.
When you read a script, alphabetic or non-alphabetic, you are recognising speech when it is written down. The new brain research shows that even before reading, children who will later experience dyslexia show differences in oral speech processing compared to other children. These differences are subtle, and are related to perceiving rhythm patterns in speech. Rhythm patterning in every language depends on variations in loudness (or amplitude) in the sound wave of speech. These loudness variations occur simultaneously at many different speeds and are naturally produced by movements of our tongues, larynx and jaw.
Perceiving some of the loudness (energy) patterns in the sound wave differently is a bit like being colour blind. If you are colour blind, you can still see, but your sensitivity to certain wavelengths of light is reduced. You cannot really distinguish reds, greens, browns and oranges, they look very similar. In dyslexia, the brain research suggests that affected children can still hear. They pass medical hearing screens and they still learn oral language, but their sensitivity to certain variations in loudness (the energy patterns governing syllable stress) is reduced. Syllables with different weight sound very similar to the dyslexic brain. For example, a person with dyslexia cannot easily distinguish whether words like “zebra” or “dinosaur” have first syllable stress. This syllable-level difficulty affects all linguistic processing, including processing of individual sounds in the syllables in words, such as the “z” in “zebra”.
These perceptual difficulties appear to arise because some of the electrical rhythms (brain waves) whose job is to record slow energy changes in speech are out of time. Dyslexic brains seem to be less accurate in recording the slower rhythm patterns present in natural speech, but not the faster rhythm patterns. The slower rhythms are those deliberately exaggerated at the beginning of language acquisition, when we use BabyTalk to infants. We can think of the dyslexic brain always coming in slightly too early (or late) in terms of catching the slower energy patterns in the signal.
So how can we help? One way is to devise methods for helping children to recognise rhythm patterns in speech before they begin learning to read. Oral language games can help children to pick out stressed syllables (the syllables carrying more acoustic weight, as in ZE-bra or DI-no-saur), or help them to count the syllables in words. Games that match drumming or tapping to syllable patterns are also beneficial, and so is learning poetry out loud or rapping. And as even infants with a family (genetic) risk for dyslexia show these acoustic processing differences, deliberately using BabyTalk as much as possible during babyhood may also be beneficial.
CBE FRS FBA is Professor of Cognitive Developmental Neuroscience at the University of Cambridge and founding Director of the Centre for Neuroscience in Education. After training as a primary school teacher, she pursued a research career. Her core interests are the neural mechanisms underpinning language acquisition and the brain basis of dyslexia.