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Deafness in children poses significant challenges to spoken language and cognitive development. Cochlear implants (CIs) provide access to speech sounds, improving spoken language acquisition and overall child development. However, children with CIs often experience delays in expressive vocabulary compared to their typically developing (TD) peers (Lund, 2016). They also demonstrate poorer cognitive skills, including working memory, which are important for language development (Lyxell, 2008). Although cochlear implantation alone is insufficient to bridge the developmental gap, early access to sound and language through early implantation and intervention can contribute positively to expressive vocabulary and overall language and cognitive abilities.
This study aimed to compare expressive vocabulary, phonological working memory (PWM) and general working memory (GWM) in children with CI and TD children. It further investigated how expressive vocabulary relates to PWM and GWM in the two groups of participants.
Twelve 8-12-year-old children, who received CIs at the mean age of 9 months, participated in the study. Ten of them received early intervention (data missing for one participant). The control group comprised 22 TD peers. All participants completed tests evaluating expressive language, PWM and GWM.
Preliminary analysis revealed that children with CIs performed comparably to their TD peers on expressive vocabulary and GWM, but not on PWM task. In both groups, expressive vocabulary did not correlate with either PWM or GWM.
The preliminary results are in line with previous studies (e.g. May-Mederake, 2012) that found age-appropriate language outcomes in early implanted children. This indicates that early implantation and intervention might have had a positive role in participants’ linguistic development. However, PWM remained impaired in children with CI, regardless of their early access to speech sound. Early experiences shape phonological development, influencing PWM through timing, as well as the quality and quantity of language input (Pierce et al., 2017). Despite advances in cochlear implant technology, these devices offer a reduced auditory signal, which, although improved, may still be somewhat impoverished. This degraded spectral-temporal information limits rehabilitative improvement, potentially impacting PWM.
While PWM has been suggested to play a significant role in vocabulary development (Baddeley, 2003), the preliminary findings raise questions about how children with CIs are able to achieve adequate vocabulary despite limited PWM skills. Gathercole et al. (1992) propose that once vocabulary is adequately developed, PWM capacity may play a less dominant role in further vocabulary acquisition. Persistently poor phonological memory skills do not seem to significantly hinder language acquisition during the early school years. GWM may have a more important role at that stage, although our preliminary results did not confirm this. An alternative explanation is that other factors, such as conceptual abilities and exposure to print, may contribute more strongly to vocabulary learning by middle childhood (Stanovich & Cunningham, 1993).
