Effects of Specific Language Impairment (SLI) and bilingualism on verbal short-term memory

The current study assessed independent and combined effects of SLI and bilingualism on tasks tapping into verbal short-term memory (vSTM) with varying linguistic load in two languages (Russian and Hebrew). The study explored the extent to which the presence of SLI is related to limited vSTM storage and bilingualism is associated with reduced vocabulary size. A total of 190 monolingual and bilingual children aged 5;5-6;8 participated in the current study: 108 sequential Russian-Hebrew bilinguals (18 with SLI), 48 Hebrew monolinguals (13 with SLI) and 34 Russian monolinguals (14 with SLI). Children performed three repetition tasks: forward-digit span (FWD), nonword repetition (NWR) and sentence repetition (SRep); bilingual children were tested in both of their languages. Results indicated a negative effect of SLI on all experimental tasks tapping into vSTM. The effect of SLI rose as a function of increased linguistic load. Regarding bilingualism, no effect was found on the measure of vSTM with the lowest linguistic load (FWD), while its effect was robust once the linguistic load was increased (SRep). The results reported in this study bring evidence that lower performance on measures of vSTM in children with SLI and bilingual children stem from different sources. Although, children with SLI have limitations of vSTM, deficient vSTM cannot fully account for the linguistic difficulties observed in children with SLI. As for bilingualism, it does not affect verbal storage when the linguistic load is minimal, while poor performance in bilingual children on tasks with greater linguistic load is attributed to smaller vocabulary sizes.