Different kinds of infants' smiles in the first six months and contingency to maternal affective behavior.

Infants' smiling is considered an expression of affection, and an index of cognitive and socio-emotional development. Despite research advances in this area, there is much to explore on the ontogeny of smiling, its meaning and the context in which it is manifested early in life. This study aimed at: (a) investigating smiling patterns in these different developmental moments in early infancy, (b) analyzing patterns of association between babies' smiles and their mothers' affective behaviors, and (c) verifying whether babies can answer contingently, with smiles, to mothers' affective behaviors. Participants were sixty Brazilian mother-infant dyads. Infants in three age levels (one, three, and five months of age) and their mothers were observed. They were videotaped at home, during 20 minutes in free sessions. The results indicate increase in frequency of infants' smiling instances across ages (F(2, 59) = 9.18, p < .05), variations in the frequency of maternal behaviors accompanying the variations in infants' smiling (F(2, 59) = 6.03, p < .05), correlations between infants' smiling and mothers' affective behaviors, and contingency between the behaviors of both mothers and infants. It was verified a strong association between mothers' behavior and their babies' smiles, emphasizing the importance of affective interactions in early stages of development.