Numerical discrimination of sets of elements by Archerfish

Debates have arisen as to whether non-human animals actually can learn abstract non-symbolic numerousness or whether they always rely on some continuous physical aspect of the stimuli, covarying with number. Here we investigated archerfish (Toxotes jaculatrix) non-symbolic numerical discrimination with accurate control for co-varying continuous physical stimulus attributes. Archerfish were trained to select one of two groups of black dots (Exp. 1: 3 vs. 6 elements; Exp. 2: 2 vs. 3 elements); these were controlled for several combinations of physical variables (elements’ size, overall area, overall perimeter, density and sparsity), ensuring that only numerical information was available. Generalization tests with novel numerical comparisons (2 vs. 3, 5 vs. 8 and 6 vs. 9 in Exp. 1; 3 vs. 4, 3 vs. 6 in Exp. 2) revealed choice for the largest or smallest numerical group according to the relative number that was rewarded at training. None of the continuous physical variables, including spatia...学界始终存在争议：非人类动物是否能够习得抽象的非符号数量表征（non-symbolic numerousness），抑或始终依赖与数量共变的刺激物某一连续物理属性。本研究以射水鱼（Toxotes jaculatrix）为研究对象，探究其非符号数量辨别（non-symbolic numerical discrimination）能力，并对与数量共变的连续物理刺激属性进行精准控制。实验中，射水鱼被训练选择两组黑点中的一组（实验1：3个与6个元素；实验2：2个与3个元素）；研究对多项物理变量组合（单个元素尺寸、总覆盖面积、总周长、密度与稀疏度）进行控制，确保仅数量信息可作为决策的唯一依据。采用全新数量对比范式开展泛化测试（实验1包含2vs3、5vs8与6vs9；实验2包含3vs4、3vs6），结果显示，射水鱼会依据训练阶段奖励所关联的相对数量，选择数量更多或更少的组别。所有连续物理变量，包括空间相关属性均未对其选择产生显著影响。