Hachmann, W. M. 1 , Postiglione, F. 1 , Cashdollar, N. M. 2 & Job, R. 1
1 Fondazione Marica De Vincenzi ONLUS, Department of Psychology and Cognitive Science, University of Trento, Italy
2 Center for Mind and Brain Sciences, University of Trento, Italy
This study joins the line of research investigating the processing of serial order information in short-term memory in dyslexic individuals. Recently, some models of short-term memory make a distinction between order and item processing, in which order information represents a domain-general function of short-term memory, whereas item information is a short-term activation of long-term memory. In a sample of dyslexic and normal reading school children, we investigated whether serial order processing problems in dyslexia are linked to a selective impairment of short-term memory for serial order, and whether this impairment affects processing in both the verbal and the nonverbal domains. Twelve dyslexic children and matched control groups for chronological age (CA) and for reading age (RA) participated in a controlled 2 (task) x 2 (material) experiment. It consisted of a double probe short-term recognition task for order (correct order of the two probes?) and item information (had both items been present?) with verbal (object drawings) and nonverbal material (nonsense symbols) respectively. Within the item conditions, half of the true probes were presented in consecutive order and the other half in opposite order. Findings indicate that all participant groups performed at the same level in each of the item tasks. But the ability to correctly identify the serial order was found to be weakest in the dyslexic group and significantly highest in CA controls. The RA control group obtained an intermediate position. Moreover, serial order information from true probes in item tasks facilitated processing in control groups, whereas there was no influence of serial order on item task performance in the dyslexic group. The results support the assumption that serial order processing in short-term memory is selectively impaired in dyslexia, and that this fact is only partly covered by co-development of reading level and serial order processing.