Quantity discrimination, the ability to discriminate a magnitude of difference or discrete numerical information, plays a key role in animal behavior. While quantitative ability has been well documented in fishes, birds, mammals, and even in previously unstudied invertebrates and amphibians, it is still poorly understood in reptiles and has never been tested in an aquatic turtle despite the fact that evidence is accumulating that reptiles possess cognitive skills and learning ability. To help address this deficiency in reptiles, we investigated the quantitative ability of an Asian freshwater turtle, Mauremys sinensis, using red cubes on a white background in a trained quantity discrimination task. While spontaneous quantity discrimination methods are thought to be more ecologically relevant, training animals on a quantity discrimination task allows more comparability across taxa. We assessed the turtles’ quantitative performance in a series of tests with increasing quantity ratios and numerosities. Surprisingly, the turtles were able to discriminate quantities of up to 9 versus 10 (ratio = 0.9), which shows a good quantitative ability that is comparable to some endotherms. Our results showed that the turtles’ quantitative performance followed Weber’s law, in which success rate decreased with increasing quantity ratio across a wide range of numerosities. Furthermore, the gradual improvement of their success rate across different experiments and phases suggested that the turtles possess learning ability. Reptile quantitative ability has long been ignored and therefore is likely under-estimated. More comparative research on numerical cognition across a diversity of species will greatly contribute to a clearer understanding of quantitative ability in animals and whether it has evolved convergently in diverse taxa.

中文翻译：

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淡水龟的优良连续数量判别

数量辨别能力，即辨别差异幅度或离散数字信息的能力，在动物行为中起着关键作用。虽然在鱼类、鸟类、哺乳动物，甚至以前未研究过的无脊椎动物和两栖动物中，定量能力已被充分记录，但在爬行动物中仍然知之甚少，并且从未在水龟中进行过测试，尽管越来越多的证据表明爬行动物具有认知能力技能和学习能力。为了帮助解决爬行动物的这一缺陷，我们在训练有素的数量辨别任务中使用白色背景上的红色立方体研究了亚洲淡水龟 Mauremys sinensis 的定量能力。虽然人们认为自发的数量区分方法在生态上更相关，在数量辨别任务上训练动物可以在分类群中具有更多的可比性。我们通过增加数量比率和数量的一系列测试评估了海龟的定量表现。令人惊讶的是，海龟能够区分多达 9 对 10 的数量（比率 = 0.9），这显示出与某些吸热动物相当的良好定量能力。我们的结果表明，海龟的数量表现遵循韦伯定律，其中成功率随着数量比例的增加而降低。此外，它们在不同实验和阶段的成功率逐渐提高表明海龟具有学习能力。爬行动物的定量能力长期以来一直被忽视，因此很可能被低估了。