Université de Rennes 1, Ethologie animale et humaine, UMR 6552 - CNRS, Station Biologique de Paimpont, Paimpont, France.
PLoS One. 2012;7(9):e45106. doi: 10.1371/journal.pone.0045106. Epub 2012 Sep 12.
Measuring the affective state of an individual across species with comparable non-invasive methods is a current challenge in animal communication research. This study aims to explore to which extent affect intensity is conveyed in the vocal behaviours of three nonhuman primate species (Campbell's monkeys, De Brazza's monkeys, red-capped mangabeys), which vary in body size, ecological niche and social system. Similarly in the three species, we experimentally induced a change in captive social groups' affect by locking all group members together in their outside enclosure. The two experimental conditions which varied in affect intensity consisted in imposing a pre-reunion 90 mn-separation by splitting up the respective group into two subgroups (High affect condition) or not (Low affect condition). We measured call rates as well as voice features at the time of reunion in both conditions. The three studied species reacted in a very similar way. Across species, call rates changed significantly between the behaviourally defined states. Furthermore, contact call duration and, to some extent, voice pitch increased. Our results suggest, for the first time in arboreal Old World monkeys, that affect intensity is conveyed reliably in vocal behaviour and specific acoustic characteristics of voice, irrespective of body size and ecological niche differences between species. Cross-taxa similarities in acoustic cues of affect intensity point to phylogenetic constraints and inheritance from a common ancestor, whereas variations in vocal behaviour and affect intensity-related acoustic cues between species may be an adaptation to specific social requirements and depend on social systems. Our findings as well as a comparison with published works on acoustic communication in other vertebrate groups support the hypothesis that affect intensity in human voice originates from precursors already found deep inside the vertebrate phylogeny.
用可比的非侵入性方法测量跨物种个体的情感状态是当前动物交流研究中的一个挑战。本研究旨在探讨三种非人类灵长类物种（坎贝尔氏长尾猴、戴帽长尾猴、红冠卷尾猴）的叫声行为在多大程度上传递了情感强度，这三种物种在体型、生态位和社会系统方面存在差异。同样在这三个物种中，我们通过将所有的群体成员一起锁在他们的外部围栏里，在圈养的社会群体中实验性地引起了情感的变化。两种实验条件在情感强度上有所不同，包括通过将各自的群体分成两个小组来强制分离 90 分钟（高情感条件）或不分离（低情感条件）。我们在两种条件下测量了团聚时的叫声率以及声音特征。三种研究的物种反应非常相似。在跨物种的情况下，叫声率在行为定义的状态之间发生了显著变化。此外，接触叫声的持续时间和在某种程度上的声音音高增加。我们的研究结果首次表明，在树栖的旧大陆猴中，情感强度可靠地传递在叫声行为和声音的特定声学特征中，而与物种之间的体型和生态位差异无关。跨类群的情感强度的声学线索的相似性表明了系统发育的限制和来自共同祖先的遗传，而物种之间的发声行为和与情感强度相关的声学线索的变化可能是对特定社会需求的适应，并取决于社会系统。我们的发现以及与其他脊椎动物类群的声学通讯的已发表作品的比较支持了这样一种假设，即人类声音中的情感强度起源于脊椎动物进化中早已存在的先驱。
