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• Correctness and speed of dyslexics and non-dyslexics on the four mathematical operations

This research describes an investigation of the correctness and speed of response that dyslexic children and matched controls perform on mathematical calculations involving addition, subtraction, multiplication and division. The participants were 120 boys divided into three age bands ranging from 9:5 - 11:4, 11:5 - 13:4 and 13:5 - 15:4 years of age of whom 60 were dyslexic and 60 non-dyslexic. Two sets of 144 multiplication sums, two sets of 75 addition and 75 subtraction sums and one set of 144 division sums were presented. In the case of multiplication and division, the numbers ranged from 1 to 12; in the case of addition and subtraction two separate effects were examined, viz. sums involving high and low addends / subtrahends in combination with sums that did and did not cross the ten barrier. Results showed that dyslexics in all age bands took longer and made fewer correct responses than non-dyslexics on all four mathematical operations. The performance of the younger dyslexics was differentially disadvantaged when compared to non-dyslexics and older dyslexics on speed and correctness. The dyslexics performed less well when no obvious algorithm was available to them and when answering questions that involved crossing the ten barrier. The dyslexics were less able, in all age bands, than non-dyslexics to respond instantaneously. The overall trend with both groups was an increase in scores with age; however on some occasions the dyslexics in the old age band did not perform as well as those in the middle-age band suggesting practice and automaticity effects. The order of difficulty (from greatest to least) of the four mathematical operations for dyslexics, as judged by number of correct responses was: division, subtraction, multiplication and addition. For the non-dyslexics this was: subtraction, division, multiplication and addition. For speed the order for both the dyslexics and non-dyslexics was: subtraction, addition, division and multiplication.