Humans have the remarkable ability to rapidly estimate the number of objects in a visual scene without relying on counting, something referred to as the number sense. It has been well documented that the more clustered the elements are, the lower their perceived numerosity is. A recent account of this observation is the crowdinghypothesis, which posits that the perceived underestimation is driven by visual crowding: the inability to recognise objects in clutter. Crowding can impair individuation of the elements, which would explain the underestimation. Here, we tested the crowding hypothesis by assessing numerosity estimation and crowding for the same stimulus configurations in the same participants. Experiment 1 compared the two tasks when numerosity can be considered to be estimated directly by the visual system (reference patch density = 0.12 items/deg2), while Experiment 2 used high density stimuli (density = 0.88 items/deg2), where numerosity may be estimated indirectly. In both cases, we found that spacing and similarity between elements affected estimation and crowding tasks in markedly different ways. These results are incompatible with a crowding account of numerosity underestimation and point to separate mechanisms for object identification and number estimation, although grouping may play a moderating role in both cases.

中文翻译：

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聚类导致对数字的低估，但拥挤不是原因。

人类具有非凡的能力，可以快速估计视觉场景中的对象数量，而无需依赖计数，这就是所谓的数字感。有充分的文献证明，元素的聚集程度越高，其感知的数字量就越低。关于这种观察的最新解释是拥挤假说，该假说认为视觉低估是由视觉拥挤驱动的：无法识别杂乱的物体。拥挤会损害要素的个性化，这可能会低估了这一点。在这里，我们通过评估数字估计和相同参与者中相同刺激配置的拥挤测试了拥挤假设。实验1比较了两个任务，这时可以通过视觉系统直接估计数字（参考贴图密度= 0。12项/度2），而实验2使用高密度刺激（密度= 0.88项/度2），其中数字可以间接估算。在这两种情况下，我们发现元素之间的间隔和相似性以明显不同的方式影响估计和拥挤任务。这些结果与数字低估的拥挤说法不符，并指出了对象识别和数字估计的单独机制，尽管在这两种情况下分组都可能起到调节作用。