Young G, Décarie T G
Anim Behav. 1977 Feb;25(1):95-107. doi: 10.1016/0003-3472(77)90071-9.
The ethological approach is suggested as a fruitful research strategy in the study of how infants express emotions. This approach led to the development of a large catalogue of facial/vocal behaviour which was used in the systematic observation of 75 girl and boy infants, who in the last quarter of the first year of life were placed in a series of standardized laboratory situations. Each of the 42 facial expressions contained in the catalogue is precisely defined according to the expressive elements of the brow, eyes, mouth and other facial regions. The vocalizations are also operationally defined. The possible ways that the facial expressions and vocalizations could be combined in the expression of emotional behaviour in infants are discussed.