The relationship between smile type and play type during parent-infant play.

This study examined the relationship between smile type and play type during parent-infant interactions in the home. Thirty-six mother-infant and father-infant dyads were videotaped playing for 10 min. Smile type (basic, Duchenne, and duplay smiles) and play type (object, physical, vocal, and book reading) were coded. Results of loglinear analysis indicated that different types of smiles occur during different types of play more often than expected if distributed equally. In addition, different smile-type and play-type patterns occurred for father-infant dyads compared with mother-infant dyads. Qualitative analyses were used to generate hypotheses about the reasons why different types of smiles occurred during various play activities.