Children with dyslexia classify pure tones slowly.

Developmental dyslexia is normally characterised by unexpected problems in learning to read for children of average or above average intelligence. Interestingly, however, slower speed of information processing appears to be a recurring symptom of dyslexia. There is a substantial literature on deficits in speed of access to the spoken word, initially discovered using the 'rapid automatised naming' test1. This test involves the rapid sequential naming of a series of 50 familiar stimuli presented simultaneously on a card. The authors showed that dyslexic children were slower to name colours, pictures, digits and letters than slow learners matched for reading age. Unfortunately, these and similar demonstrations of reduced speed of information processing have involved linguistic processing, and it is therefore not clear whether the deficit represents another correlate of the known linguistic abnormalities of dyslexic children or whether reduced speed of information processing reflects some deeper problem. Five groups of children participated: 14 dyslexic children around 15 years old; 11 dyslexic children around 11 years old; 11 non-dyslexic children matched to the older dyslexic children for age and full IQ; 12 non-dyslexic children of similar IQ to the two dyslexic groups, matched for reading age with the older dyslexic children and for chronological age with the younger dyslexic children; and 9 non-dyslexic children matched for full IQ and reading age with the younger dyslexic children. All the dyslexic children had been diagnosed between the ages of 7 and 10, based on discrepancies of at least 18 months between actual and reading age. Their IQ levels fell in the normal to superior range on the Wechsler Intelligence Scale for Children and they had no known neurological deficit or primary emotional difficulty. In pilot studies we established that dyslexic children showed the expected speed deficit in complex linguistically-based tasks. Consequently, in an attempt to find normal performance, we administered increasingly simple tasks — lexical decision, choice reaction, and finally simple reaction to a tone. In the lexical decision task, subjects were presented auditorily with a word (or, equally probably, a morphologically valid nonword) and had to say as quickly as possible Yes (if it was a word) or No (if it was a nonword). The dependent variable of interest was the response latency. In both reaction time experiments, subjects sat with a single button in their preferred hand, and their task was to press it as quickly as possible whenever they heard a low …