Humans can use an intuitive sense of statistics to make predictions about uncertain future events, a cognitive skill that underpins logical and mathematical reasoning. Recent research shows that some of these abilities for statistical inferences can emerge in preverbal infants and non-human primates such as apes and capuchins. An important question is therefore whether animals share the full complement of intuitive reasoning abilities demonstrated by humans, as well as what evolutionary contexts promote the emergence of such skills. Here, we examined whether free-ranging rhesus macaques (Macaca mulatta) can use probability information to infer the most likely outcome of a random lottery, in the first test of whether primates can make such inferences in the absence of direct prior experience. We developed a novel expectancy-violation looking time task, adapted from prior studies of infants, in order to assess the monkeys' expectations. In Study 1, we confirmed that monkeys (n = 20) looked similarly at different sampled items if they had no prior knowledge about the population they were drawn from. In Study 2, monkeys (n = 80) saw a dynamic 'lottery' machine containing a mix of two types of fruit outcomes, and then saw either the more common fruit (expected trial) or the relatively rare fruit (unexpected trial) fall from the machine. We found that monkeys looked longer when they witnessed the unexpected outcome. In Study 3, we confirmed that this effect depended on the causal relationship between the sample and the population, not visual mismatch: monkeys (n = 80) looked equally at both outcomes if the experimenter pulled the sampled item from her pocket. These results reveal that rhesus monkeys spontaneously use information about probability to reason about likely outcomes, and show how comparative studies of nonhumans can disentangle the evolutionary history of logical reasoning capacities.

中文翻译：

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恒河猴使用概率来预测未来事件

人类可以使用统计的直觉来预测不确定的未来事件，这是一种支持逻辑和数学推理的认知技能。最近的研究表明，其中一些统计推断能力可以出现在会说话的婴儿和非人类灵长类动物（如猿和卷尾猴）中。因此，一个重要的问题是动物是否拥有人类展示的全部直觉推理能力，以及哪些进化背景促进了这种技能的出现。在这里，我们检查了自由放养的恒河猴（Macaca mulatta）是否可以使用概率信息来推断随机抽奖的最可能结果，这是第一次测试灵长类动物是否可以在没有直接先前经验的情况下做出此类推断。我们开发了一种新颖的预期违反时间任务，改编自先前对婴儿的研究，以评估猴子的期望。在研究 1 中，我们证实，如果猴子 (n = 20) 对不同的样本项目没有先验知识，那么它们对不同的样本项目的看法相似。在研究 2 中，猴子（n = 80）看到了一个包含两种水果结果混合的动态“彩票”机器，然后看到更常见的水果（预期的试验）或相对稀有的水果（意外的试验）从机器。我们发现猴子在目睹意外结果时看起来更长。在研究 3 中，我们证实这种影响取决于样本和总体之间的因果关系，而不是视觉错配：如果实验者从她的口袋里掏出样本物品，猴子（n = 80）会同等地看待这两种结果。这些结果表明，恒河猴会自发地使用有关概率的信息来推理可能的结果，并表明对非人类的比较研究如何解开逻辑推理能力的进化史。