Data_Sheet_1_Resources Underlying Visuo-Spatial Working Memory Enable Veridical Large Numerosity Perception.docx

Humans can quickly approximate how many objects are in a visual image, but no clear consensus has been achieved on the cognitive resources underlying this ability. Previous work has lent support to the notion that mechanisms which explicitly represent the locations of multiple objects in the visual scene within a mental map are critical for both visuo-spatial working memory and enumeration (at least for relatively small numbers of items). Regarding the cognitive underpinnings of large numerosity perception, an issue currently subject to much controversy is why numerosity estimates are often non-veridical (i.e., susceptible to biases from non-numerical quantities). Such biases have been found to be particularly pronounced in individuals with developmental dyscalculia (DD), a learning disability affecting the acquisition of arithmetic skills. Motivated by findings showing that DD individuals are also often impaired in visuo-spatial working memory, we hypothesized that resources supporting this type of working memory, which allow for the simultaneous identification of multiple objects, might also be critical for precise and unbiased perception of larger numerosities. We therefore tested whether loading working memory of healthy adult participants during discrimination of large numerosities would lead to increased interference from non-numerical quantities. Participants performed a numerosity discrimination task on multi-item arrays in which numerical and non-numerical stimulus dimensions varied congruently or incongruently relative to each other, either in isolation or in the context of a concurrent visuo-spatial or verbal working memory task. During performance of the visuo-spatial, but not verbal, working memory task, precision in numerosity discrimination decreased, participants’ choices became strongly biased by item size, and the strength of this bias correlated with measures of arithmetical skills. Moreover, the interference between numerosity and working memory tasks was bidirectional, with number discrimination impacting visuo-spatial (but not verbal) performance. Overall, these results suggest that representing visual numerosity in a way that is unbiased by non-numerical quantities relies on processes which explicitly segregate/identify the locations of multiple objects that are shared with visuo-spatial (but not verbal) working memory. This shared resource may potentially be impaired in DD, explaining the observed co-occurrence of working memory and numerosity discrimination deficits in this clinical population.

人类能够快速估算视觉图像中的物体数量，但目前学界对于支撑这一能力的认知机制尚未达成明确共识。过往研究支持如下观点：在心理地图中显性表征视觉场景内多个物体位置的机制，对视空间工作记忆（visuo-spatial working memory）与计数（至少针对相对少量物体）均至关重要。针对大数量知觉的认知基础，当前颇具争议的一个问题是：为何数量估算往往并不准确（即易受非数量特征的偏差影响）。这类偏差在发展性计算障碍（developmental dyscalculia, DD）群体中尤为显著——该学习障碍会影响算术技能的习得。
鉴于已有研究发现DD群体同样常存在视空间工作记忆损伤，我们提出假设：支持该类型工作记忆的资源（可同时识别多个物体），或许同样对精准且无偏差的大数量知觉至关重要。因此我们验证了：在健康成人被试完成大数量辨别任务期间加载工作记忆负荷，是否会加剧非数量特征带来的干扰。
被试需对多刺激阵列完成数量辨别任务，其中数值与非数值刺激维度可独立或在并发视空间/言语工作记忆任务的背景下，呈现一致或不一致的变化。在完成视空间工作记忆任务（而非言语工作记忆任务）期间，被试的数量辨别精度下降，其选择会显著受到物体大小的偏差影响，且该偏差强度与算术技能测评结果呈相关关系。此外，数量知觉与工作记忆任务间的干扰具有双向性：数量辨别会影响视空间（而非言语）工作记忆的任务表现。
综上，本研究结果表明：不受非数量特征偏差影响的视觉数量表征，依赖于与视空间工作记忆（而非言语工作记忆）共享的、显性分离/识别多个物体位置的认知过程。这一共享资源在DD群体中可能存在损伤，这或许可以解释该临床群体中同时出现的工作记忆与数量辨别缺陷。