DeWind Nicholas K, Brannon Elizabeth M
Department of Psychology, University of Pennsylvania, Philadelphia PA, USA.
Front Psychol. 2016 Mar 8;7:310. doi: 10.3389/fpsyg.2016.00310. eCollection 2016.
The approximate number system (ANS) is the hypothesized cognitive mechanism that allows adults, infants, and animals to enumerate large sets of items approximately. Researchers usually assess the ANS by having subjects compare two sets and indicate which is larger. Accuracy or Weber fraction is taken as an index of the acuity of the system. However, as Clayton et al. (2015) have highlighted, the stimulus parameters used when assessing the ANS vary widely. In particular, the numerical ratio between the pairs, and the way in which non-numerical features are varied often differ radically between studies. Recently, Clayton et al. (2015) found that accuracy measures derived from two commonly used stimulus sets are not significantly correlated. They argue that a lack of inter-test reliability threatens the validity of the ANS construct. Here we apply a recently developed modeling technique to the same data set. The model, by explicitly accounting for the effect of numerical ratio and non-numerical features, produces dependent measures that are less perturbed by stimulus protocol. Contrary to their conclusion we find a significant correlation in Weber fraction across the two stimulus sets. Nevertheless, in agreement with Clayton et al. (2015) we find that different protocols do indeed induce differences in numerical acuity and the degree of influence of non-numerical stimulus features. These findings highlight the need for a systematic investigation of how protocol idiosyncrasies affect ANS assessments.
近似数字系统（ANS）是一种假设的认知机制，它使成年人、婴儿和动物能够大致枚举大量物品。研究人员通常通过让受试者比较两组物品并指出哪一组数量更多来评估近似数字系统。准确性或韦伯分数被用作该系统敏锐度的指标。然而，正如克莱顿等人（2015年）所强调的，在评估近似数字系统时使用的刺激参数差异很大。特别是，两组之间的数值比率以及非数值特征的变化方式在不同研究中往往有很大差异。最近，克莱顿等人（2015年）发现，从两个常用刺激集得出的准确性测量结果没有显著相关性。他们认为，缺乏测试间的可靠性会威胁到近似数字系统结构的有效性。在此，我们将一种最近开发的建模技术应用于同一数据集。该模型通过明确考虑数值比率和非数值特征的影响，产生的相关测量结果受刺激方案的干扰较小。与他们的结论相反，我们发现两个刺激集的韦伯分数存在显著相关性。然而，与克莱顿等人（2015年）的观点一致，我们发现不同的方案确实会在数字敏锐度以及非数值刺激特征的影响程度上产生差异。这些发现凸显了对实验方案特性如何影响近似数字系统评估进行系统研究的必要性。
