In his discussion of amodal perception, vitality affects and their contribution to maternal attunement, Stern seeks to illuminate the process through which the infant begins to understand the relatedness between the self and other. Stern defined affect attunement as the behavioral expression of the quality of feeling of a common affect state. Taken together, amodal perception and vitality affects are best understood as preconditions for the achievement of affect attunement between mother and child.
Amodal perception refers to the natural ability of the infant to receive information from one sensory modality and then interpret it in another. Stern cites a number of studies that support this idea of cross-modal matching. Three week old infants, for example, are able to visually discern which of two nipples they have just sucked while blindfolded. Amodal properties such as shape, intensity, motion and rhythm serve as a kind of “common currency” between sensory modalities. Furthermore, information is not encoded to a particular mode, but is rather programmed into an amodal representation which can be distinguished by any sensory mode.
Stern conceives vitality affects as “dynamic shifts or patterned changes” in the self or others which involve qualities of feeling that are not best portrayed by the vocabulary used to describe what he terms categorical affects, such as sadness or joy. He describes, for example, the “rush” associated with anger, or that evoked by music or abstract dance. Infants are thought to categorize the actions of the caregiver (such as how she picks up the infant or folds diapers) in terms of vitality affects, and a range of sensory experiences with comparable “activation contours” are experienced as analogous and organizing. The amodal experience of vitality affects and the ability for matching across modes, according to Stern, furthers the infant’s progress toward understanding the “emergent other”.
In the process of attunement, amodal perception occurs between mother and infant during what Stern calls an “intersubjective exchange”, wherein the mother reads the internal feeling state of the child and acts out a variation of behavior that relates to it. The infant then interprets her behavior as relevant to his own original internal experience. As a result of the mother’s attuning, the child is allowed the experience of “being with” another and we as adults are reminded that intimate, internal feeling states are something that can be shared and communicated even on such a nonverbal level.