Vitality affects and amodal perception are key components of Stern’s concept of affect attunement. Taken together, they are what really distinguish it from similar ideas like affect mirroring and affect matching. One of the defining characteristics of affect attunement is its cross-modality of expression. The baby makes a verbal expression and the parent acknowledges and reflects it with a corresponding body movement. This differentiates attunement from simple imitation, the parent’s response corresponding to the baby’s inner experience and intention rather than her outer expression. (When Fonagy & Target talk about marked affect mirroring in relation to the development of reflective functioning, I think this is part of what they mean. Simple imitation of the baby’s affect might be threatening or flooding—the parent’s response must be “marked,” possibly by a change or partial change in mode of expression, so that it acknowledges the feeling instead of the behavior.) This cross-modality wouldn’t make sense to the baby without the ability to perceive amodally, that is, to meaningfully relate percepts from one sensory modality to those from another.
Stern describes what he calls “vitality affects” because he isn’t satisfied with the usual range of affects that others have dealt within the context of parent-child relations. What he terms categorical affects—sadness, anger, etc.—can indeed be attuned to, but they only occur sporadically. Affect attunement, however, is a continuous process which “feels like an unbroken line.” To fill in the gaps, we have vitality affects, which are occurring all the time, though not necessarily consciously. The attuned parent tracks the subtle moment-to-moment changes in a baby’s internal rhythm and intensity.
The centrality of vitality affects in attunement was recently highlighted for me in the experience of being with a sick baby. How does one attune to a child who does little but lie still? There was little opportunity to mirror categorical affect during Annie’s illness, and in any case one cannot spend the whole day making sad faces. But obviously there was affect in her, which could be perceived in the sluggishness of her movements, her glazed eyes, and her utter lack of intensity. As I reflect on it, I see that the slow throb of Annie’s painful experience was reflected in the tempo of my hand patting her back and the whisper that I used when holding her. None of it is particularly remarkable; these are the things any parent would do, and as Stern points out, they happen with almost no conscious thought.