Department of Developmental Psychology and Socialization, University of Padova, Padova, Italy.
Department of General Psychology, University of Padova, Padova, Italy.
Dev Sci. 2024 Nov;27(6):e13538. doi: 10.1111/desc.13538. Epub 2024 Jul 1.
Impaired numerosity perception in developmental dyscalculia (low "number acuity") has been interpreted as evidence of reduced representational precision in the neurocognitive system supporting non-symbolic number sense. However, recent studies suggest that poor numerosity judgments might stem from stronger interference from non-numerical visual information, in line with alternative accounts that highlight impairments in executive functions and visuospatial abilities in the etiology of dyscalculia. To resolve this debate, we used a psychophysical method designed to disentangle the contribution of numerical and non-numerical features to explicit numerosity judgments in a dot comparison task and we assessed the relative saliency of numerosity in a spontaneous categorization task. Children with dyscalculia were compared to control children with average mathematical skills matched for age, IQ, and visuospatial memory. In the comparison task, the lower accuracy of dyscalculics compared to controls was linked to weaker encoding of numerosity, but not to the strength of non-numerical biases. Similarly, in the spontaneous categorization task, children with dyscalculia showed a weaker number-based categorization compared to the control group, with no evidence of a stronger influence of non-numerical information on category choice. Simulations with a neurocomputational model of numerosity perception showed that the reduction of representational resources affected the progressive refinement of number acuity, with little effect on non-numerical bias in numerosity judgments. Together, these results suggest that impaired numerosity perception in dyscalculia cannot be explained by increased interference from non-numerical visual cues, thereby supporting the hypothesis of a core number sense deficit. RESEARCH HIGHLIGHTS: A strongly debated issue is whether impaired numerosity perception in dyscalculia stems from a deficit in number sense or from poor executive and visuospatial functions. Dyscalculic children show reduced precision in visual numerosity judgments and weaker number-based spontaneous categorization, but no increasing reliance on continuous visual properties. Simulations with deep neural networks demonstrate that reduced neural/computational resources affect the developmental trajectory of number acuity and account for impaired numerosity judgments. Our findings show that weaker number acuity in developmental dyscalculia is not necessarily related to increased interference from non-numerical visual cues.
发展性计算障碍（低“数字敏锐度”）患者的数量感知受损，被解释为支持非符号数量感的神经认知系统表示精度降低的证据。然而，最近的研究表明，较差的数量判断可能源于非数值视觉信息的更强干扰，这与强调执行功能和视空间能力受损在计算障碍发病机制中的替代解释一致。为了解决这一争论，我们使用了一种心理物理学方法，旨在在点比较任务中分离数字和非数字特征对显式数量判断的贡献，并在自发分类任务中评估数量的相对显著性。与具有平均数学技能且年龄、智商和视空间记忆相匹配的对照组儿童相比，计算障碍儿童接受了评估。在比较任务中，与对照组相比，计算障碍儿童的较低准确性与数量的编码较弱有关，但与非数值偏差的强度无关。同样，在自发分类任务中，与对照组相比，计算障碍儿童的基于数量的分类较弱，没有证据表明非数值信息对类别选择的影响更强。使用数量感知的神经计算模型进行的模拟表明，代表性资源的减少会影响数量敏锐度的逐步细化，对数量判断中非数值偏差的影响很小。总之，这些结果表明，计算障碍中的数量感知受损不能用非数值视觉提示的干扰增加来解释，从而支持核心数量感缺陷的假设。研究亮点：一个备受争议的问题是，计算障碍中的数量感知受损是源于数量感缺陷还是执行功能和视空间功能差。计算障碍儿童在视觉数量判断中表现出较低的精度和较弱的基于数量的自发分类，但对连续视觉属性的依赖程度没有增加。使用深度神经网络进行的模拟表明，减少神经/计算资源会影响数量敏锐度的发展轨迹，并解释了受损的数量判断。我们的研究结果表明，发展性计算障碍中较弱的数量敏锐度不一定与非数值视觉提示的干扰增加有关。
