How sleeping neonate smile

Infants over one month of age tend to produce two types of smiling during especially positive social interactions, Duchenne smiles involving cheek raising and open-mouth smiles. Little is known, however, about the prevalence, frequency, duration and organization of these smiles among neonates. Twenty-five full-term, healthy neonates (12 female) were videotaped during six minutes of sleep. Smiles were identified and analysed using an anatomically based coding system (FACS/Baby FACS). One-half of the neonates showed bilateral Duchenne smiles. One-quarter of the neonates showed bilateral Duchenne smiles at a mature level of intensity whose median duration was 1 1/3 s. By contrast, open-mouth bilateral smiles occurred in less than one-tenth of the sample. The contrast between the more frequent bilateral Duchenne smiles and the less frequent open-mouth smile is discussed in terms of the early synergistic functioning of facial muscles and contrasted with the smiling patterns of older infants.