Darkeyeddog_data_Study2.csv from Are dark-eyed dogs favoured by humans? Domestication as a potential driver of iris colour difference between dogs and wolves

Comparative studies have shown that the eye morphology of primates has been shaped by a variety of selection pressures (e.g. communication, environmental factors). To comprehensively elucidate the complex links between ocular morphology and its evolutionary drive, attention should be paid to other phylogenetic groups. Here, we address a new question regarding the evolution of eye colour patterns in the oldest domesticated animal, namely, the domestic dog (Canis familiaris). In this study, we conducted an image analysis of dogs and their closest relatives, grey wolves (Canis lupus), to compare the colours of their irises, with the aim of assessing whether eye colours of dogs affect how humans perceived dogs. We found that the irises of dogs were significantly darker than those of wolves. We also found that facial images of dark-eyed dogs were perceived as more friendly and immature, potentially eliciting caregiving responses from humans. Our findings are consistent with our expectation that humans favour dark-eyed dogs over light-eyed ones and provide an updated hypothesis that dogs with dark eyes may have evolved by acquiring a facial trait that sends a non-threatening gaze signal to humans.

对比研究表明，灵长类动物的眼部形态受到多种选择压力（如交流需求、环境因素）的塑造。为全面阐明眼部形态与其演化驱动因素之间的复杂关联，应将研究目光投向其他系统发育类群。本研究针对最古老的驯化动物——家犬（Canis familiaris）的眼色模式演化提出全新研究问题。本研究对家犬及其近缘物种灰狼（Canis lupus）开展图像分析，以比较二者虹膜颜色差异，旨在探究家犬的眼色是否会影响人类对其的认知评价。研究结果显示，家犬的虹膜颜色显著深于灰狼。此外，本研究还发现，深色虹膜的家犬面部图像会被人类感知为更具亲和力且更显幼态，进而可能激发人类的抚育行为。本研究结果与我们的预期相符，即人类更偏好深色虹膜的家犬；同时我们提出更新后的假说：深色虹膜家犬的演化，可能是通过获得向人类传递无威胁凝视信号的面部特征实现的。