Asymmetrical interference between number and item size perception provides evidence for a domain specific impairment in dyscalculia
Asymmetrical interference between number and item size perception provides evidence for a domain specific impairment in dyscalculia
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DOI：
10.1371/journal.pone.0209256
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发表时间：
2018-12-14
期刊：
影响因子：
3.7
通讯作者：
Eger, Evelyn
中科院分区：
文献类型：
--
作者：
Castaldi, Elisa;Mirassou, Anne;Eger, Evelyn
计算障碍是一种影响算术技能的特殊学习障碍，以前一直被认为与估计视觉场景中物体的大致数量的系统(所谓的数字感觉系统)的精确度不足有关。然而，由于在涉及数量比较的任务中，计算障碍者的判断似乎不成比例地受到连续数量维度(如项目的大小)的影响，另一种观点将计算障碍与抑制与任务无关的反应的领域普遍困难联系起来。为了在这些观点之间进行仲裁，我们评估了成人计算障碍患者和配对对照组中数字和非数字数量维度之间的相互干扰程度。我们使用了一种新的刺激集，该刺激集的平均项目大小和数量都是垂直变化的，特别注意匹配这两个特征的感知区分能力。参与者根据这两个维度的每一个对这些刺激进行了比较。控制组被试在判断个数时没有表现出显著的大小干扰，而计算障碍者的个数判断受到无人注意的大小维度的强烈偏向。然而，重要的是，两组在判断平均大小时，都表现出了来自无人照管维度的相同程度的干扰。此外，只有在比较数字时丢弃不相关的大小信息的能力(而不是相反的能力)才能显著预测受试者的计算能力。总体而言，我们的结果表明，当另一个数量特征(平均项目大小)的感知辨别能力匹配时，数字辨别比另一个量化特征(平均项目大小)的辨别更不容易受到干扰，就像在这里的对照受试者中一样。通过第一次量化计算障碍受试者在同一刺激的另一个正交维上的干扰程度，我们能够排除域一般抑制缺陷作为他们糟糕/有偏见的数字判断的解释。我们认为，在数字辨别过程中加强对非数字线索的依赖可以代表一种应对不太精确的数字感觉的策略。
Dyscalculia, a specific learning disability that impacts arithmetical skills, has previously been associated to a deficit in the precision of the system that estimates the approximate number of objects in visual scenes (the so called 'number sense' system). However, because in tasks involving numerosity comparisons dyscalculics' judgements appears disproportionally affected by continuous quantitative dimensions (such as the size of the items), an alternative view linked dyscalculia to a domain-general difficulty in inhibiting task-irrelevant responses. To arbitrate between these views, we evaluated the degree of reciprocal interference between numerical and non-numerical quantitative dimensions in adult dyscalculics and matched controls. We used a novel stimulus set orthogonally varying in mean item size and numerosity, putting particular attention into matching both features' perceptual discriminability. Participants compared those stimuli based on each of the two dimensions. While control subjects showed no significant size interference when judging numerosity, dyscalculics' numerosity judgments were strongly biased by the unattended size dimension. Importantly however, both groups showed the same degree of interference from the unattended dimension when judging mean size. Moreover, only the ability to discard the irrelevant size information when comparing numerosity (but not the reverse) significantly predicted calculation ability across subjects. Overall, our results show that numerosity discrimination is less prone to interference than discrimination of another quantitative feature (mean item size) when the perceptual discriminability of these features is matched, as here in control subjects. By quantifying, for the first time, dyscalculic subjects' degree of interference on another orthogonal dimension of the same stimuli, we are able to exclude a domain-general inhibition deficit as explanation for their poor/biased numerical judgement. We suggest that enhanced reliance on non-numerical cues during numerosity discrimination can represent a strategy to cope with a less precise number sense.