Verbal working memory and linguistic long-term memory: Exploring the lexical cohort effect

The effect of schistosomiasis and soil-transmitted helminths on expressive language skills among African preschool children

Background

Schistosomiasis and soil transmitted helminths (STH) have been associated with compromised child development. We determined the effect of schistosomiasis and STH on expressive language skills among isiZulu speaking preschool children focusing on the variables: age, gender, school and stunting.

Methods

We quantitatively compared the performance of a cohort of infected and non-infected children using a 2 phased approach. In phase 1 infected children were treated with praziquantel and matched with non-infected children and both groups were tested for expressive language performance. In phase 2 both groups of children were re-tested for expressive language skills using a similar but modified test. The participants were 106 preschool children between the age of 4 and 6 years, 11 months. The Developmental Language Test was adapted as a linguistically and culturally appropriate tool for assessing isiZulu expressive language skills.

Results

The overall performance of the children in phases 1 and 2 were statistically similar. There was significant Pearson’s correlation of expressive language skills to age (0.002, P < 0.01), schistosomiasis i.e. vocabulary 1 (0.024, P < 0.05) and narrative skills (0.001, P < 0.01) and soil-transmitted helminths i.e. vocabulary 1 (0.006, P < 0.05), colours (0.029, P < 0.05) and narrative skills (0.001, P < 0.01) in phase 2 with small to high Cohen’s d effect size for various language subtests.

Conclusion

We concluded that even mild schistosomiasis and STH may compromise the performance of preschool children on expressive language. However poor ability in following instructions may have contributed to general poor performance across the two groups tested. Diet, school effect and stunting did not influence the performance of the children on expressive language.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07260-2.

EXPRESS: The Company a Word Keeps: The Role of Neighbourhood Density in Verbal Short-Term Memory

Psycholinguistic information plays an important role in verbal memory over the short-term (vSTM). One such linguistic feature is neighbourhood density (ND)-the number of words that can be derived from a given word by changing a single phoneme or single letter-so that vSTM performance is better when word sequences are from dense rather than sparse neighbourhoods, an effect attributed to higher levels of supportive activation among neighbouring words. Generally, it has been assumed that lexical variables influence item memory but not order memory, and we show that the typical vSTM advantage for dense neighbourhood words in serial recall is eliminated when using serial recognition. However, we also show that the usual effect of ND is reversed-for both serial recall and serial recognition-when using a subset of those same words. The findings call into question the way in which ND has been incorporated into accounts of vSTM that invoke mutual support from long-term representations on either encoding or retrieval.