Smiling and laughing as communication in humans and non-human primates

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K21128
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Cognitive science; Educational psychology
• Research Institution: Chubu University (2018-2019); Kyoto University (2016-2017)
• Principal Investigator: Kawakami Fumito 中部大学, 人文学部, 講師 (80723064)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 笑顔 / 非言語コミュニケーション / 新生児 / チンパンジー / ニホンザル / 動物園

Outline of Final Research Achievements

Why are human smiles unique? Neonates show spontaneous smiling, i.e., smiling without any external stimuli, during irregular sleep. Moreover, the frequency of social smiling increases from around two-months of age in both humans and chimpanzees. I observed human infants, captive chimpanzees, and captive infant Japanese macaques. The main results indicated that infant Japanese macaques, similar to humans, show spontaneous smiling. Furthermore, chimpanzees displayed social smiling in only two situations: when playing, and when infant chimpanzees were lifted by their mothers. These observations suggest that the early development of smiling and laughter in humans and non-human primates have commonalities, although smiling in chimpanzees might be limited to playful situations. Also, chimpanzees might not be sensitive to smiling by other chimpanzees. Humans might be unique in showing frequent smiling under a variety of situations, and in sharing pleasant emotions with others by smiling.

Free Research Field

比較認知発達科学

Academic Significance and Societal Importance of the Research Achievements

ヒトにとって日々の生活の中で頻繁に表出し，みる機会のある笑顔は，あまりに一般的であるため，実は謎が多く残されていることはそれほど知られていない。笑顔について進化と発達の視点から探った研究が少ないのが現状である。どのように笑顔を対他者関係の中で使い，それがどのくらい社会関係の維持に寄与しているのだろうか。多くの場合において快感情のあらわれとして使われる笑顔を探求することは，ヒトやチンパンジーを含む動物にとって，よりよい環境を築く足がかりとなると考えられる。