All smiles are positive but some smiles are more positive than others

Disagreement as to whether all smiling or specific types of smiling index p ositive emotion early in life was addressed by examining when infants produ ced different types of smiling and other facial expressions. Thirteen infan ts were observed weekly from 1 to 6 months of age. Smiling alone-without ch eek raising or mouth opening-was relatively more likely than periods withou t smiling both when mothers were smiling and when infants were gazing at th eir mothers' faces. Cheek-raise (Duchenne) smiling was relatively more like ly than smiling alone only when mothers were smiling. Open-mouth (play) smi ling was relatively more likely than smiling alone only when infants were g azing directly at mothers' faces. Smiling involving both cheek raising and mouth opening was relatively likely both when mothers were smiling and when infants were gazing at mothers' faces and became increasingly likely with age when both conditions co-occurred. The cheek-raise and open-mouth dimens ions of smiling appear to be associated with, respectively, the amplificati on of processes of sharing positive affect and of visual engagement that ar e present to a lesser degree in smiling alone.