Measures of Working Memory Span and Verbal Rehearsal Speed in Deaf Children after Cochlear Implantation

Abstract

In Brief Large individual differences in spoken word recognition performance have been found in deaf children after cochlear implantation. Recently, Pisoni and Geers (2000) reported that simple forward digit span measures of verbal working memory were significantly correlated with spoken word recognition scores even after potentially confounding variables were statistically controlled for. The present study replicates and extends these initial findings to the full set of 176 participants in the CID cochlear implant study. The pooled data indicate that despite statistical “partialling-out” of differences in chronological age, communication mode, duration of deafness, duration of device use, age at onset of deafness, number of active electrodes, and speech feature discrimination, significant correlations still remain between digit span and several measures of spoken word recognition. Strong correlations were also observed between speaking rate and both forward and backward digit span, a result that is similar to previously reported findings in normal-hearing adults and children. The results suggest that perhaps as much as 20% of the currently unexplained variance in spoken word recognition scores may be independently accounted for by individual differences in cognitive factors related to the speed and efficiency with which phonological and lexical representations of spoken words are maintained in and retrieved from working memory. A smaller percentage, perhaps about 7% of the currently unexplained variance in spoken word recognition scores, may be accounted for in terms of working memory capacity. We discuss how these relationships may arise and their contribution to subsequent speech and language development in prelingually deaf children who use cochlear implants. Although previous articles in this supplement have examined child, family, implant, and educational variables that account for significant variance in outcome, these factors account for only about half of the total variance. These authors maintain that to explain further variance we must focus on the underlying cognitive information processing skills that are used to support the perception and production of spoken language. Estimates of working memory capacity and articulation rate were obtained for 176 children with cochlear implants using the digit span scores from the Wechsler Intelligence Scale for Children and speaking rate measurements from productions of the McGarr sentences. Results indicate that a substantial portion of the currently unexplained variance may be independently accounted for by individual differences in working memory capacity and other cognitive factors related to the speed and efficiency with which phonological and lexical representations of spoken words are maintained in and retrieved from working memory.