| Systematic study of the emergence of phonological categories in infancy requires a distinction between raw phonological material (RM), acoustic/phonetic variation within phonological categories, and negotiable phonological product (NPP), phonological categories formed from variable raw material. In this framework, infants are seen as creating phonological categories in the process of vocally exploring acoustic/phonetic dimensions. Observing the distinction between RM and NPP in early vocal development will help bring into focus the functional development of early communicative vocalizations. In the laboratory, only the details of RM are identified when researching infant vocalizations. It is imperative to illuminate the role caregivers play in identifying infant phonological categories. Caregivers recognize negotiable categories against the background of variable RM pronunciations by the infant, when particular acoustic/phonetic features are consolidated by the infant (e.g., as manifested in repetition). NPP represents those vocal categories produced with sufficient repetitiveness and consequent identifiability, that they are recognized by caregivers as negotiable---that is, as possible vehicles for communication.;Distinguishing between RM and NPP, and incorporating caregiver interpretation of infant vocalizations into theories of phonological development, may provide us with a clearer view of the primary patterns of functional phonological development. The goal of this work is to offer both a theoretical perspective and foundational methodologies to allow realistic estimates of functional phonological repertoire sizes in infant vocalizations. Results are drawn from caregiver, naturalistic listener, and transcriber perceptions of infant vocalizations taken from 20-minute recording sessions of eight infants at three ages (8, 10, and 12 months). Results indicate that manipulating listening opportunities within the laboratory changes the way in which coders perceive infant phonological repertoires. Caregivers and coders provided with listening opportunities designed to be relatively similar to those of caregivers, perceived smaller syllable inventories than coders provided with listening circumstances that allowed for more attention to detail. The perceived differences in repertoire sizes for the different listening circumstances supports the conceptual difference between RM and NPP, and supports the need to incorporate caregiver interpretation of infant phonological categories into observation of developmental patterns. |
