Magnitude-Space Representations in the N-Back Task: Long-Term Representations of Magnitudes Alter the Working Memory Performance

Abstract

Prior research has predominantly examined the role of working memory (WM) in tasks involving numerical information and spatial properties, such as memorizing number sequences and performing parity judgment and magnitude comparison. In contrast to focusing solely on the effect of WM on number judgment tasks, our study investigates how magnitude-space associations affect WM task performance, emphasizing long-term representations, specifically the concept of mental number line (MNL) compatibility (small items on the left, large items on the right) in long-term memory (LTM). Moving from the idea of representations within LTM contribute to the functioning of WM during task execution, we explore the effects of congruent, incongruent, and negative congruent numerical and non-numerical magnitude-space associations on magnitude-based 1-back (low WM load) and 2-back (high WM load) tasks. MNL compatible n-back and test items are congruent, MNL compatible n-back and MNL incompatible (small on the right, large on the left) test items (or vice versa) are incongruent, and MNL incompatible n-back and test items are considered negative congruent. Because negative congruent and incongruent representations may not activate existing representations in LTM, as congruent representations, we expected worse WM performance in negative congruent and incongruent trials than in congruent trials. Results reveal that congruent and incongruent representations elicit more accurate and rapid responses than negative congruents, suggesting that congruent and incongruent representations contribute to task execution. Additionally, we observe a size effect for small numerical magnitudes and a reverse size effect for large physical magnitudes, pointing towards the coactivation of LTM and WM in magnitude-space relations.