VOCALIZING IN UNISON AND IN ALTERNATION: TWO MODES OF COMMUNICATION WITHIN THE MOTHER‐INFANT DYAD *

Two laboratories studying dyadic communication have joined in a n ongoing research project on the ontogeny of communication. One laboratory has engaged in the study of naturally occurring interactions between mothers and infants, particularly their “nonverbal” communication.’-6 The other has focused on the rhythm of adult Together, we are examining vocal and kinesic behaviors and their integration during the course of development. This paper presents a part of that ongoing study. During the first half-year of life the infant communicates effectively through a variety of behaviors: head and body movement and tone, gaze, facial expressions, and vocalizations. By the age of three to four months, all of these behaviors can be integrated to form recognizable complex expressive acts. The distinction between vocal and other motor acts is less compelling at this point in development, and in fact, if made too sharply, may obscure a view of early vocalization. For instance, when watching a film of an infant, with the sound turned off, it is impossible to predict reliably when he is vocalizing. In social situations, there exists a wide range and variety of mouth behaviors, especially mouth-opening with head thrown up, which are extremely expressive and evocative.4 These may or may not be accompanied by a vocalization. When a vocalization is added to the entire kinesic event, that event becomes importantly different. Nonetheless, infant vocalizations rarely occur (in a social situation) as an isolated motor act such as an adult can perform in speaking; rather, they occur as another element in the constellation of kinesic events that make up a communicative act. Furthermore, they occur within an interpersonal context in which the levels of arousal and affective tone are constantly changing. We thus have examined mother and infant vocalization from the viewpoint that they are sound-producing kinesic events, as well as prelinguistic events which later transform into speech. This paper was initially prompted by an unexpected finding. During play sessions, mothers and their threeto four-month-old infants vocalize simultaneously to a far greater extent than we had anticipated or than had been commented on in the literature. Early vocalizations appear to have at least one beginning within the motherinfant dyad as a coaction system in which each member is performing the same or similar behavior a t the same time. This occurrence of behavioral coaction between