How does a caregiver communicate (or shall I say ‘commune’?) to her prelinguistic baby that she understands and is attuned to her baby’s subjective inner state? And perhaps more importantly, how does the infant extract meaning from this interaction? The intersubjective exchange of affective states, according to Stern, requires the caregiver to grasp the baby’s feeling state based on the baby’s behavior (Stern initially states that the baby’s behavior must be “overt,” but later includes those more ambiguous expressions that are not simply categorical affective expressions). Next, the caregiver must reciprocate and reflect back the baby’s behavior without merely replicating the baby’s behavior. Finally, the baby must interpret the caregiver’s behavior as a genuine reaction (not merely an imitation) to the infant’s subjective feeling state. Stern argues that vitality affects and amodal perception are the mechanisms by which this intersubjective affect exchange happens.
Research has demonstrated that babies have amodal perception capacities that allow them to perceive variations in intensity, time and shape with multiple sensory modalities. For instance, babies are able to match visual and auditory levels of intensity as demonstrated by an experiment where infants matched variations in sound to variations in brightness of lights. You may be wondering what this physiological ability has to do with affect attunement. On the surface, the connection isn’t so clear, but upon further examination it becomes apparent that in order for the baby to communicate with the mother, it is necessary for the baby to “speak” cross-modally. In other words, a mother’s mirror neurons may kick in and she may react to her baby screeching in glee to the sight of a puppy, by patting the baby’s bottom with the same kind of intensity that the baby originally exuded. This attunement is cross-modal, of course, and it allows the intersubjective sharing of affect to occur.
The preceding example of the baby’s overt glee to the sight of a puppy illustrates a categorical affective expression that obviously conveys happiness. But how does the caregiver pick up on the more common, less overt behavioral expressions of affective states? This is where vitality affects come into play. Vitality Affects are defined as elusive qualities of feelings that occur constantly in contrast to more discrete categorical affects. It seems that vitality affects initially get subconsciously picked up on by the caregiver through perceptual/amodal means (e.g., speed of movement), but then transform into feeling states that attune the caregiver to the baby’s subjective inner state. This attunement is ultimately an interpersonal communion between caregiver and baby, and allows the mother to engage in the baby’s inner experience without impinging on or altering the baby’s inner experience.