Compared Duchenne and non-Duchenne smiles of 1- to 6-month olds during weekly videotapes of mother/infant interaction for clues regarding emotional significance. Correlated levels of Duchenne and non-Duchenne smiling within sessions; found that they had similar developmental trajectories. Duchenne smiles were typically preceded by non-Duchenne smiles. Findings suggest that these smiles are often different temporal phases of a continuous emotional process. (Author)