What's in a smile?

In positive social contexts, both adults and older infants show more Duchen ne smiling (which involves high cheek raising) than non-Duchenne smiling (w hich does not). This study compared Duchenne and non-Duchenne smiles in ear ly infancy for clues to their emotional significance. Infants (N = 13) from 1 to 6 months of age were videotaped weekly for 5 min in 208 face-to-face interactions with their mothers. Levels of Duchenne and non-Duchenne smilin g were correlated within interactive sessions, and the 2 smiles had similar developmental trajectories. Duchenne smiles were typically preceded by non -Duchenne smiles. The results suggest these frequently contrasted types of smiles occur in similar situations and are often different temporal phases of a continuous emotional process. In contrast to adults, infant Duchenne s miles had longer durations than non-Duchenne smiles, suggesting infant smil ing does not fit adult models of emotional functioning.