Although researchers have debated whether a core deficit of nonsymbolic representation of magnitude underlies developmental dyscalculia (DD), research has mostly focused on numerosity processing. We probed the possibility of a general magnitude deficit in individuals with DD and asked whether sensitivity to size varied in contexts of depth ordering and size constancy. We measured full psychometric functions in size-discrimination tasks in 12 participants with DD and 13 control participants. Results showed that although people with DD exhibited veridical perceived magnitude, their sensitivity to size was clearly impaired. In contrast, when objects were embedded in depth cues allowing size-constancy computations, participants with DD demonstrated typical sensitivity to size. These results demonstrate a deficit in the perceptual resolutions of magnitude in DD. At the same time, the finding of an intact size constancy suggests that when magnitude perception is facilitated by implicit mandatory computations of size constancy, this deficit is no longer evident.

尽管研究人员一直在争论非符号表示的核心缺陷是否是发育性计算障碍 (DD) 的基础，但研究主要集中在数字处理上。我们探讨了 DD 个体普遍存在幅度缺陷的可能性，并询问对尺寸的敏感性是否在深度排序和尺寸恒定性的背景下有所不同。我们测量了 12 名 DD 参与者和 13 名对照参与者在大小区分任务中的完整心理测量功能。结果表明，尽管患有 DD 的人表现出真实的感知幅度，但他们对尺寸的敏感性明显受损。相比之下，当对象嵌入允许大小恒定计算的深度线索中时，DD 参与者表现出对大小的典型敏感性。这些结果表明 DD 量级的感知分辨率存在缺陷。同时，完整大小恒常性的发现表明，当大小恒常性的隐式强制计算促进了幅度感知时，这种缺陷不再明显。