Leinwand individual plots exp 1-3.R from Familiarity mediates apes' attentional biases toward human faces

In zoos, primates experience markedly different interactions with familiar humans, such as the zookeepers who care for them, compared to those with unfamiliar humans, such as the large volume of zoo visitors to whom they are regularly exposed. While the behaviour of zoo-housed primates in the presence of unfamiliar, and to a lesser extent familiar, humans have received considerable attention, if and how they spontaneously distinguish familiar from unfamiliar people, and the cognitive mechanisms underlying the relationships they form with familiar and unfamiliar humans, remain poorly understood. Using a dot-probe paradigm, we assessed whether primates (chimpanzees and gorillas) show an attentional bias toward the faces of familiar humans, with whom the apes presumably had a positive relationship. Contrary to our predictions, all subjects showed a significant attentional bias toward unfamiliar people's faces compared to familiar people's faces when the faces showed a neutral expression, both with and without a surgical face mask on, but no significant attentional bias when the faces showed a surprised expression. These results demonstrate that apes can spontaneously categorize humans based on familiarity and we argue that the attentional biases the apes showed for unfamiliar human faces reflect a novelty effect.

在动物园环境中，灵长类动物（primates）与熟悉人类（如照料自身的动物园饲养员）的互动模式，与它们和陌生人类（如日常频繁接触的大量游客）之间存在显著差异。尽管学界已对动物园圈养灵长类在陌生人类（以及程度稍低的熟悉人类）在场时的行为开展了大量研究，但这些类人猿是否会自发区分熟悉与陌生人类，以及它们与熟悉、陌生人类建立关系背后的认知机制，目前仍知之甚少。本研究采用点探测范式（dot-probe paradigm），评估了灵长类动物（黑猩猩与大猩猩）是否会对熟悉人类的面孔产生注意偏向——假定这些类人猿与熟悉人类存在积极互动关系。与我们的预测相悖，当面孔呈现中性表情时，无论是否佩戴外科口罩（surgical face mask），所有受试对象均对陌生人类面孔表现出显著的注意偏向；而当面孔呈现惊讶表情时，则未出现显著注意偏向。本研究结果证实，类人猿能够基于熟悉度自发对人类进行分类；我们认为，类人猿对陌生人类面孔表现出的注意偏向，反映了一种新奇性效应（novelty effect）。