关键词: 数量感知, 分组化策略, 分组线索, 拓扑知觉理论, 功能磁共振成像

Abstract: Numerosity perception refers to the human cognitive ability to extract numerical information from various stimuli. It serves as a fundamental basis for understanding the world and processing information, thereby guiding and influencing human behavior and decision-making. Grouping strategies, also known as "groupitizing," involve organizing objects into sets or categories during numerosity perception processes. This facilitates a rapid and effective numerosity estimation, particularly in situations with short presentation times and numerous quantities. Groupitizing combines the advantages of subitizing and counting, thereby influencing individual arithmetic abilities. Previous studies have predominantly focused on investigating the groupitizing of numerosity perception based on intrinsic grouping cues. However, the influence of both intrinsic and extrinsic cues of perceptual grouping on numerosity perception during groupitizing remains underexplored. Previous studies spanning the visual and numerosity perception domains have consistently indicated that extrinsic grouping cues exhibit stronger grouping advantages than intrinsic ones. Therefore, this study employed a numerosity estimation task to separately examine the effects of intrinsic (such as color similarity and proximity) and extrinsic grouping cues (including common region and connectedness) on numerosity perception during groupitizing. This study aimed to uncover the neural mechanisms underlying groupitizing.
A total of 21 university students were recruited for this study. A block design was employed for the functional magnetic resonance imaging (fMRI) task. Stimulus presentation and generation were performed using MATLAB's PsychToolbox (version R2016b). The stimuli comprised four factors: grouping condition (grouping, no-grouping), grouping cues (extrinsic, intrinsic), and numerosity (6, 9, 12, 16). MRI scans for the numerosity estimation task were conducted using Siemens 3.0 T technology, synchronously collecting functional brain data. The participants were instructed to select the corresponding number of points they estimated based on the stimuli presented on the screen. We compared functional activation between grouping and no-grouping conditions, as well as between extrinsic and intrinsic grouping cues. Additionally, we employed the Pearson product-moment correlation method to assess the relationships between these variables.
The results revealed that first, bilateral intraparietal sulcus (IPS) plays a critical role in numerosity perception, particularly showing significant activation during the quantity processing stage. Specifically, activation was observed in the IPS during numerosity perception tasks, indicating its involvement in processing numerical information. Second, both grouped and ungrouped conditions activated cortical regions associated with quantity estimation, such as the precentral gyrus and inferior temporal gyrus. Under the grouped condition, additional activation was observed in brain regions related to computation; this includes the superior frontal gyrus, IPS, and angular gyrus, exhibiting a left-hemisphere lateralization advantage. Thus, participants tended to utilize computational and retrieval strategies in the grouped condition compared to that in the ungrouped condition, suggesting a more efficient processing mechanism. Lastly, extrinsic grouping cues, relative to intrinsic grouping cues, activate additional brain regions associated with topological properties, such as the middle frontal and inferior temporal gyrus. This reveals the topological invariance characteristic of extrinsic grouping cues in the intrinsic mechanism of numerosity perception grouping strategies, highlighting the influence of extrinsic cues on neural processing mechanisms.
This study’s findings suggest that participants tended to rely more on mental arithmetic and factual retrieval when employing grouping strategies to enhance numerosity perception efficiency. This sheds further light on why grouping strategies are comparatively more efficient than other approaches. Moreover, the mechanism of extrinsic grouping cues in numerosity perception strategies demonstrates topological invariance, which presents a unique advantage in perceptual processing. This discovery provides direct neural evidence of the significance of topological properties in numerosity perception, thereby deepening our understanding of numerosity perception and its neural underpinnings.

Key words: Numerosity perception, Groupitizing, Grouping cues, Topological perception theory, fMRI