Animal Behaviour & Welfare, Animal and Veterinary Sciences Research Group, Scotland's Rural College (SRUC), West Mains Road, Edinburgh, EH9 3JG, UK.
Institute of Animal Husbandry and Animal Welfare, Department of Farm Animals and Veterinary Public Health, University for Veterinary Medicine Vienna, Veterinärplatz 1, 1210, Vienna, Austria.
Sci Rep. 2018 Dec 4;8(1):17602. doi: 10.1038/s41598-018-35905-3.
Facial expressions convey information on emotion, physical sensations, and intent. The much debated theories that facial expressions can be emotions or signals of intent have largely remained separated in animal studies. Here we integrate these approaches with the aim to 1) investigate whether pigs may use facial expressions as a signal of intent and; 2) quantify differences in facial metrics between different contexts of potentially negative emotional state. Facial metrics of 38 pigs were recorded prior to aggression, during aggression and during retreat from being attacked in a dyadic contest. Ear angle, snout ratio (length/height) and eye ratio from 572 images were measured. Prior to the occurrence of aggression, eventual initiators of the first bite had a smaller snout ratio and eventual winners showed a non-significant tendency to have their ears forward more than eventual losers. During aggression, pigs' ears were more forward orientated and their snout ratio was smaller. During retreat, pigs' ears were backwards and their eyes open less. The results suggest that facial expressions can communicate aggressive intent related to fight success, and that facial metrics can convey information about emotional responses to contexts involving aggression and fear.
面部表情传达了情感、身体感觉和意图的信息。关于面部表情可以是情绪还是意图的信号的理论在动物研究中一直存在很大争议，这些理论在很大程度上是分开的。在这里，我们将这些方法结合起来，目的是 1）研究猪是否可能将面部表情作为意图的信号；2）量化潜在负面情绪状态的不同情境下面部指标的差异。在二元竞争中，在攻击之前、攻击期间和从被攻击中撤退期间，记录了 38 头猪的面部指标。从 572 张图像中测量了耳角、口鼻比（长度/高度）和眼比。在攻击发生之前，最初发起第一口的猪的口鼻比更小，最终的获胜者比最终的失败者更倾向于将耳朵向前转。在攻击过程中，猪的耳朵向前倾斜，口鼻比变小。在撤退期间，猪的耳朵向后，眼睛睁开的幅度更小。结果表明，面部表情可以传达与战斗成功相关的攻击意图，并且面部指标可以传达与涉及攻击和恐惧的情境相关的情绪反应信息。
