Lavelli, M., & Fogel, A. (2005). Developmental changes in the relationship between the infant’s attention and emotion during early face-to-face communication: The 2-month transition. Developmental Psychology, 41, 265-280. doi: 10.1037/0012-1649.41.1.265
Abstract.Weekly observations documented developmental changes in mother-infant face-to-face communication between birth and 3 months. Developmental trajectories for each dyad of the duration of infant facial expressions showed a change from the dominance of Simple Attention (without other emotion expressions) to active and emotionally positive forms of attention to the mother toward the end of the 2nd month. The results support an overlapping waves model, rather than a stage model, of developmental change. Sequential analysis found developmental changes from cycling between Gaze Elsewhere and Simple Attention to the Mother’s Face in the early weeks to a complex sequence of transitions between Concentrated Attention, Smile, and Cooing Expression nested into sequences of positive communication during the 2nd and 3rd months.
https://www.researchgate.net/profile/Manuela_Lavelli/research