This paper argues that infants' affect patterns are innate and are meaningful indicators of individual differences in internal state. Videotapes of seven infants' faces were coded using an ethogram; the movement of the eyebrow, eye direction, eye openness, mouth shape, mouth position, lip position, and tongue protrusion were assessed independently. Nearly the whole range of facial movements was observed during the neonatal period, thus indicating that all the movements generally called smile, frown, angry grimace, excitement, boredom, sorrow, joy and shame are possible from at least the second or third week of life. Electrocardiogram data were recorded simultaneously with videotaping of the infants' faces during periods when the infants were attending to novel stimuli and were habituating to these stimuli. Analysis of these data revealed substantial co-occurrence of facial change and heart rate change, which suggests that observed infant affect is a reflection of the infants' internal state rather than a random patterning waiting to be organized. (Author)