title: Origins of smile and laughter: a preliminary study.
abstract: To present fundamental data, spontaneous smiles and spontaneous laughs (smiles accompanied by vocal sounds) were cross-sectionally observed in 10 newborn infants and longitudinally observed in six infants. Unilateral spontaneous smiles were more common than bilateral smiles in neonates, but by 2 months almost all spontaneous smiles were bilateral. All spontaneous laughs were bilateral. "Spontaneous smile" and "Spontaneous laugh" might be different behaviors from the beginning.
authors.affiliation: University of the Sacred Heart, 4-3-1, Hiroo, Shibuya-ku, Tokyo 150-8938, Japan. kawakami@u-sacred-heart.ac.jp
authors.forename: Kiyobumi
authors.initials: K
authors.lastname: Kawakami
authors.forename: Kiyoko
authors.initials: K
authors.lastname: Takai-Kawakami
authors.forename: Masaki
authors.initials: M
authors.lastname: Tomonaga
authors.forename: Juri
authors.initials: J
authors.lastname: Suzuki
authors.forename: Tomiyo
authors.initials: T
authors.lastname: Kusaka
authors.forename: Takashi
authors.initials: T
authors.lastname: Okai
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007845:Laughter / Q000502:physiology*; D008297:Male; D012904:Smiling / Q000502:physiology*; D013060:Speech