The present study aimed to investigate if the white-eared opossum under natural conditions is capable of spontaneously solving the parallel string task. The experimental study with this primitive mammal was carried out on fifteen naïve animals of both sexes in northeastern Brazil. The parallel strings task was arranged in apparatuses with a vertical and a horizontal arrangement. A food reward (a slice of banana) was connected at the extremity of one string. A total of 505 videos were recorded using trap cameras. Despite the observed interest in obtaining the bait, the number of attempts to reach it and the use of the strings as support (trying to directly reach the bait in the vertical apparatus), the individuals were unable to pull any of the strings, suggesting that they could not understand the problem. The present study points to the relevance of using the species Didelphis albiventris and other species from this family (e.g., D. virginiana) to broaden our knowledge about the cognitive capacity of mammalian species. In addition, the opossums might represent an advisable path to better understand the evolution of cognition in this group.

中文翻译：

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白耳负鼠不能理解平行弦的任务：在自然条件下研究原始哺乳动物。

本研究旨在调查自然条件下的白耳负鼠是否能够自发地解决平行弦任务。对这种原始哺乳动物的实验研究是在巴西东北部对15种男女幼稚的动物进行的。平行弦任务被布置在具有垂直和水平布置的设备中。在一根细绳的末端连接了一个食物奖励（一片香蕉）。使用陷井摄像机总共记录了505个视频。尽管观察到对获得诱饵的兴趣，尝试达到诱饵的次数以及使用细绳作为支撑（试图在垂直设备中直接达到诱饵）的意愿，但个人无法拉动任何细绳，这表明他们无法理解问题。Didelphis albiventris和该家族的其他物种（例如，D。virginiana），以拓宽我们对哺乳动物物种认知能力的认识。此外，负鼠可能是更好地了解这一群体认知发展的一条明智途径。