Digit span in dyslexia: variations according to language comprehension and mathematics skills

The aim of this study was to investigate digit span performance in dyslexia. It was hypothesised that differences would be found in accordance with subgrouping by language comprehension and mathematic skills, and by analyses of how the digit span scores were attained. Two digit span tasks were given to a group of dyslexic children and controls (n = 57), mean age 12.62 (SD = 1.43). The tasks were "Digit Span" of the WISC-R, and "Digit Span 2," where the use of back-up strategies like finger counting and lip reading were restricted. As expected, the digit span scores were significantly lower in the dyslexia group than in the control group. Restrictions of back-up strategies did not alter the scores in the control group, while the scores were lowered in the dyslexia group. Further analyses of longest digit span, serial recall, and serial position indicated different retrieval patterns in the subgroups. The subgroup with good language comprehension and mathematic skills (n = 12), showed impaired serial recall especially in backward recall. The subgroup with good language comprehension skills, but with mathematics impairment (n = 9), showed impaired serial recall in both forward and backward recall. The subgroup with language impairments (n = 16), recalled fewer digits than the two other subgroups. The findings were discussed in relation to the "Phonological loop" of the Multi Component Model of Working Memory, and implications for intervention were discussed.