Data from: Capuchins, space, time, and memory – an experimental test of what-where-when memory in wild monkeys

There is considerable controversy about the existence, extent and adaptive value of integrated mental maps in non-human animals. Building on prior results showing that wild capuchin monkeys in Argentina appear to recall both the location and amount of food at patches previously visited, I tested whether they also track and use elapsed time as a basis for decisions about what feeding patches to visit. I presented them with an experimental array of 8 feeding sites, at each of which food rewards increased with increasing elapsed time since the previous visit, similar to the pattern of ripe fruit accumulation in natural feeding trees. Over the course of 68 days, comprising two distinct renewal rate treatments, one group repeatedly visited sites in the feeding array, generating 212 valid choices between sites. Comparison of observations against simulated movements and hierarchical statistical models shows that the monkeys’ choices were most consistent with dynamic memory for elapsed time specific to each of the 8 sites. Thus, it appears that capuchin monkeys possess and use integrated memories of prior food patch use, including where the patch is relative to their current location, how productive the patch is, and how long it has been since they last visited the patch. Natural selection to use such integrated memories in foraging tasks may provide an ecologically-relevant basis for the evolution of complex intelligence in primates.

学界对于非人类动物是否存在整合式心理地图（integrated mental maps）、其覆盖范围以及适应价值这一问题，尚存广泛争议。本研究依托此前的研究成果——阿根廷野生卷尾猴能够回忆起此前造访过的觅食斑块（feeding patch）的位置与食物存量——测试了这些卷尾猴是否同样会追踪并利用流逝时长，作为选择觅食斑块的决策依据。研究团队设置了包含8个觅食位点的实验阵列，每个位点的食物奖励量会随上次造访后的流逝时长增加而提升，该模式与自然觅食树上成熟果实的累积规律高度相似。实验周期共68天，包含两种截然不同的更新速率处理条件，一组卷尾猴反复造访实验阵列中的位点，共得到212组有效的位点选择数据。将观测结果与模拟移动轨迹及层级统计模型（hierarchical statistical models）进行对比后发现，卷尾猴的选择行为与它们对8个位点各自的流逝时长的动态记忆模式最为吻合。由此可见，卷尾猴拥有并会运用针对过往觅食斑块使用情况的整合式记忆，其中包括该斑块相对于自身当前位置的方位、该斑块的食物丰度，以及上次造访该斑块至今的时长。在觅食活动中运用这类整合式记忆所经历的自然选择压力，或许为灵长类复杂智能的演化提供了具备生态学相关性的理论基础。