Spatial working memory load affects counting but not subitizing in enumeration
DOI: 10.3758/s13414-011-0135-5
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Summary
This study investigates whether the cognitive process of subitizing—the rapid and accurate enumeration of small numbers of items (typically up to four)—relies on the capacity limits of visual working memory. Previous research established that both subitizing range and visual working memory capacity are limited to approximately four items, suggesting a potential shared mechanism. The authors tested the hypothesis that if subitizing depends on working memory, imposing a concurrent working memory load should reduce the subitizing range or degrade enumeration efficiency within that range. To test this, Shimomura and Kumada conducted dual-task experiments where participants performed an enumeration task (counting green dots) concurrently with either a spatial working memory task (remembering locations of gray squares) or a nonspatial visual working memory task (remembering shapes of objects). Experiment 1 focused on spatial working memory, while Experiment 2 focused on nonspatial visual features. The design included dual-task conditions alongside single-task controls (enumeration alone and memory alone) to establish baseline performance. Participants enumerated between one and eight items while maintaining memory items in mind. Reaction times (RTs) and error rates were analyzed to determine the subitizing range (identified by a flat RT slope for low numerosities) and counting efficiency (identified by a linear RT increase for higher numerosities). The results demonstrated that spatial working memory load significantly affected the slope of the counting function, indicating that counting larger sets relies on spatial working memory resources. However, the spatial load did not affect subitizing performance, subitizing range, or the efficiency of enumeration for items within the subitizing range (one to three items). Similarly, nonspatial visual working memory load in Experiment 2 affected neither enumeration efficiency nor subitizing range. Across all experiments, the subitizing range remained constant at approximately four items regardless of the imposed memory load. Furthermore, the efficiency of subitizing, indexed by the RT slope for low numerosities, was not degraded by concurrent memory tasks. These findings indicate that subitizing is functionally independent of both spatial and nonspatial visual working memory capacities. While counting larger numbers of items requires the maintenance of item locations in spatial working memory, the rapid enumeration of small sets does not draw upon these same resources. This dissociation challenges the hypothesis that subitizing limits are determined by working memory capacity constraints. Instead, the results support the view that subitizing operates via a distinct mechanism, such as the FINST (fingers of instantiation) system, which allows for parallel tracking of up to four items without engaging the limited capacity of visual working memory.
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | Crossref | — | — | 1 | 2026-06-11 |
| archive | success | canonical_url | — | — | 1 | 2026-06-25 |
| extract | success | pdftotext | — | — | 2 | 2026-06-26 |
| clean | success | clean | — | — | 1 | 2026-06-26 |
| chunk | success | chunk | — | — | 1 | 2026-06-26 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-26 |
| enrich | success | semantic_scholar | — | — | 5 | 2026-07-05 |
| promote | success | — | — | — | 1 | 2026-06-11 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 1 | 2026-06-25 |
| tag | success | vector_similarity | — | — | 6 | 2026-06-26 |
| verify | success | — | — | — | 1 | 2026-06-26 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-25; verification: verified.
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