Interactional preludes to infants' affective climax - Mother-infant interaction around infant smiling in two cultures.

Due to limited research on cross-cultural similarities and differences in the development of infant smiling, the main goals of this study were to analyze, first, the development of infants' bouts of intense smiling during their third month and, second, the interactional preludes to infants' affective climax in two cultural contexts, namely Kichwa families from the Ecuadorian Andes region and educated urban middle-class families from Münster, Germany, which differ concerning their cultural models on infant smiling. Based on a longitudinal, naturalistic study design, mother-infant interaction in Kichwa (n = 10) and Münster (n = 10) families was analyzed when infants were 9 and 13 weeks old. Following a mixed methods approach, a quantitative analysis of infant smiling based on a 1-second interval-coding approach showed that there was a significant increase in infants' high-intensity positive affect from 9 to 13 weeks in the Münster, but not the Kichwa sample, leading to significant cross-cultural differences at 13 weeks.