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.