Can nonhuman animals learn abstract concepts? This intriguing question has been extensively studied over the past several decades with many different species and experimental methods. Here, we review evidence showing that pigeons can acquire a same–different concept: they readily learn to discriminate between arrays of same and different items as well as robustly transfer their discrimination to novel arrays of items. To do so, pigeons use the degree of visual variability in the collection of items, as measured by entropy. Not only pigeons, but baboons and human adults also use entropy in their discrimination of same from different items. Thus, entropy does seem to lie at the root of this basic abstract concept.

非人类动物可以学习抽象概念吗？在过去的几十年中，已经用许多不同的物种和实验方法对这一有趣的问题进行了广泛的研究。在这里，我们回顾了表明鸽子可以获得相同概念的证据：他们很容易学会区分相同和不同的物品，并将其辨别力可靠地转移到新颖的物品上。为了做到这一点，鸽子在收集物品时会使用视觉可变性的程度（通过熵来衡量）。不仅鸽子，狒狒和成年人类也使用熵来区分不同物品。因此，熵似乎确实是这个基本抽象概念的根源。