Mulcahy Nicholas J, Schubiger Michèle N, Suddendorf T
School of Psychology, University of Queensland, St. Lucia, Australia.
J Comp Psychol. 2013 Feb;127(1):109-13. doi: 10.1037/a0028621. Epub 2012 Jun 11.
Great apes appear to have limited knowledge of tool functionality when they are presented with tasks that involve a physical connection between a tool and a reward. For instance, they fail to understand that pulling a rope with a reward tied to its end is more beneficial than pulling a rope that only touches a reward. Apes show more success when both ropes have rewards tied to their ends but one rope is nonfunctional because it is clearly separated into aligned sections. It is unclear, however, whether this success is based on perceptual features unrelated to connectivity, such as perceiving the tool's separate sections as independent tools rather than one discontinuous tool. Surprisingly, there appears to be no study that has tested any type of connectivity problem using natural tools made from branches with which wild and captive apes often have extensive experience. It is possible that such ecologically valid tools may better help subjects understand connectivity that involves physical attachment. In this study, we tested orangutans with natural tools and a range of connectivity problems that involved the physical attachment of a reward on continuous and broken tools. We found that the orangutans understood tool connectivity involving physical attachment that apes from other studies failed when tested with similar tasks using artificial as opposed to natural tools. We found no evidence that the orangutans' success in broken tool conditions was based on perceptual features unrelated to connectivity. Our results suggest that artificial tools may limit apes' knowledge of connectivity involving physical attachment, whereas ecologically valid tools may have the opposite effect.
当面对涉及工具与奖励之间物理连接的任务时，大猩猩似乎对工具功能的了解有限。例如，它们不明白拉动末端系有奖励的绳子比拉动仅接触奖励的绳子更有益。当两根绳子末端都系有奖励，但其中一根绳子因明显分成对齐的部分而无法使用时，大猩猩的成功率更高。然而，尚不清楚这种成功是否基于与连接性无关的感知特征，比如将工具的不同部分视为独立的工具而非一个不连续的工具。令人惊讶的是，似乎没有研究使用野生和圈养大猩猩经常有丰富经验的树枝制成的天然工具来测试任何类型的连接性问题。有可能这种生态上有效的工具可能会更好地帮助受试者理解涉及物理连接的连接性。在这项研究中，我们用天然工具和一系列连接性问题测试了红毛猩猩，这些问题涉及奖励在连续和断裂工具上的物理连接。我们发现，与使用人工工具而非天然工具进行类似任务测试时其他研究中的猿类不同，红毛猩猩理解了涉及物理连接的工具连接性。我们没有发现证据表明红毛猩猩在断裂工具条件下的成功是基于与连接性无关的感知特征。我们的结果表明，人工工具可能会限制猿类对涉及物理连接的连接性的了解，而生态上有效的工具可能会有相反的效果。
