Individual differences in semantic short-term memory capacity and reading comprehension

We report three correlation studies, which investigate the hypothesis that individual differences in the capacity of a semantic shortterm memory (STM) component in working memory (WM) predict performance on complex language tasks. To measure the capacity of semantic STM, we devised a storage-only measure, the conceptual span, which makes use of a category-cued recall procedure. In the first two studies, where the conceptual span was administered with randomized words (not blocked by categories), we found that conceptual span predicted single-sentence and text comprehension, semantic anomaly detection and verbal problem solving, explaining unique variance beyond non-word and word span. In some cases, the conceptual span explained unique variance beyond the reading span. Conceptual span correlated better with verbal problem solving than reading span, suggesting that a storage-only measure can outperform a storage-plus-processing measure. In Study 3, the conceptual span was administered with semantically clustered lists. The clustered span correlated with the comprehension measures as well as the non-clustered span, indicating that the critical process is memory maintenance and not semantic clustering. Moreover, we found an interaction between subjects’ performance on the conceptual span and the effect of the distance between critical words in anomaly detection, supporting the proposal that semantic STM maintains unintegrated word meanings.