The first smile: spontaneous smiles in newborn Japanese macaques (Macaca fuscata)

详细信息    查看全文

• 作者：Fumito Kawakami ; Masaki Tomonaga ; Juri Suzuki
• 关键词：Smiles ; Emotion ; Neonates ; Allometric timing constancy
• 刊名：Primates
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：58
• 期：1
• 页码：93-101
• 全文大小：
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Zoology; Animal Ecology; Behavioral Sciences; Evolutionary Biology;
• 出版者：Springer Japan
• ISSN：1610-7365
• 卷排序：58

文摘

Spontaneous smiles are facial movements that are characterized by lip corner raises that occur during irregular sleep or drowsiness without known external or internal causes. They are shown by human infants and infant chimpanzees. These smiles are considered to be the developmental origin of smiling and laughter. There are some case studies showing that spontaneous smiles occur in Japanese macaques. The goals of this study were to investigate whether newborn Japanese macaques show a considerable number of spontaneous smiles thus to examine the mechanism of them. Seven newborn Japanese macaques were observed in a room for an average of 44 min, and incidental sleeping situations were monitored twice. All seven participants showed spontaneous smiles at least once during the observation. They showed 8.29 spontaneous smiles in average (SD = 10.89; 58 smiles in total), all found in the state of REM sleep. Thirty-nine of the 58 smiles were produced on the left side of the mouth. These characteristics were similar to those of spontaneous smiles in human infants. This is the first evidence that macaques as well as hominoids show a considerable number of spontaneous smiles. These phenomena may facilitate the development of the zygomaticus major muscle, which is implicated in smiling-like facial expressions.