The Semantic Similarity Effect on Short-Term Memory: Null Effects of Affectively Defined Semantic Similarity.

Studies on short-term memory have repeatedly demonstrated the beneficial effect of semantic similarity. Although the effect seems robust, the aspects of semantics targeted by these studies (e.g., categorical structure, associative relationship, or dimension of meaning) should be clarified. A recent meta-regression study inspired by Osgood's view, which highlights affective dimensions in semantics, introduced a novel index for quantifying semantic similarity using affective values. Building on the results of the meta-regression of past studies' data with that index, this study predicts that semantic similarity is deleterious to short-term memory if it is manipulated by affective dimensions, after controlling for other confounding factors. This prediction was directly tested. The experimental results of the immediate serial recall task (Study 1) and immediate serial reconstruction of order task (Study 2) indicated null effects of semantic similarity by affective dimensions and thus falsified the prediction. These results suggest that semantic similarity based on affective dimensions is negligible.

The detrimental effect of semantic similarity in short-term memory tasks: A meta-regression approach.

The literature suggests that semantic similarity has a weak or null effect for immediate serial reconstruction and a facilitative effect for immediate serial recall. These observed semantic similarity effects are inconsistent with the assumptions of short-term memory (STM) models on the detrimental effect of similarity (e.g., confusion) and with observations of a robust detrimental effect of phonological similarity. Our review indicates that the experimental results are likely dependent on the manipulation strength for semantic similarity and that manipulations used in previous studies might have affected semantic assvociation as well as semantic similarity. To address these possible issues, two indices are proposed: (a) strength of manipulation on semantic similarity, gained by quantifying semantic similarity based on Osgood and associates' dimensional view of semantics, and (b) inter-item associative strength, a possible confounding factor. Our review and the results of a meta-regression analysis using these two indices suggest that semantic similarity has a detrimental effect on both serial reconstruction and serial recall, while semantic association, which is correlated with semantic similarity, contributes to an apparent facilitative effect. An effect that is not attributable to similarity or association was also implied. Review on item and order memory further suggests the facilitative effect of semantic association on item memory and the detrimental effect of the semantic similarity on order memory. Based on our findings, we propose a unified explanation of observations of semantic similarity effects for both serial reconstruction and serial recall that is in good accord with STM models.

Person-based organisation in working memory.

Working memory (WM) helps maintain information during a variety of cognitive activities in scholastic and social situations. This study focused on a social aspect of WM, specifically, how it maintains information related to people. We investigated person-based organisation of information across four experiments using the reading span task (RST). Person information (i.e., an occupational title) was provided with sentences manipulated across conditions. In Experiment 1, consistent with the assumption that person-based organisation exists in WM, participants performed better when they could easily organise target items in a person-based manner (person-based organisation) than when they were prevented from using such information. Experiments 2 and 3 investigated the process of person-based organisation using alphabetical letters as targets (unlike words in Experiment 1), which prevented possible semantic associations between person information and target items. Experiment 2 replicated Experiment 1, suggesting that contextual retrieval is critical in person-based organisation. Experiment 3 showed the person-based organisation effect even after controlling for the difficulty of the process component in the RST. The results of Experiments 2 and 3 suggest that person information could serve as contextual retrieval cues in WM. Experiment 4, which did not show the organisation effect based on information about an object (i.e., a fruit name), suggests along with Experiments 1 to 3 that the observed organisation effect in Experiments 1 to 3 was specific to person information. In addition to showing the enhanced WM performance by person-based organisation, we have suggested contextual cue-dependent retrieval as the underlying cognitive process.