Are Max-Specified Infant Facial Expressions During Face-to-Face Interaction Consistent With Differential Emotions Theory?

Differential emotions theory (DET) proposes that infant facial expressions of emotions are differentiated. To test this hypothesis, we examined infant facial expressions longitudinally at 2, 4, and 6 months of age during face-to-face play and a "still-face" interaction with their mothers. Infant expressions were coded using the Maximally Discriminative Facial Movement Coding System (Max). Consistent with DET, discrete positive expressions occurred more of the time and were of longer duration than blended expressions of positive affect. Contrary to DET, at no age did the proportions or durations of discrete and blended negative expressions differ, and they showed different patterns of developmental change. One is led to either reject or revise DET or else question the adequacy of the Max system.