Effect of Visual and Spatial Working Memory Load on Subitizing and Estimation.

Subitizing-the rapid and accurate enumeration of small quantities-has traditionally been viewed as a pre-attentive process. This study investigates whether subitizing depends on working memory resources using a dual-task paradigm. In two experiments, participants completed enumeration tasks under visual and spatial working memory load, with encoding time manipulated across experiments. Results showed that subitizing range and accuracy declined under spatial load when presentation time was brief, while longer response times emerged under high load when timing was unconstrained. These findings partially support the hypothesis that subitizing relies on shared attentional and memory resources and align with recent evidence suggesting attentional involvement in subitizing. We propose a hybrid model in which subitizing operates through specialized but context-sensitive mechanisms.