Beyond ba-ba and gu-gu: challenges and strategies in coding infant vocalizations.

Infant vocal behaviors are extremely complex. Consequently, coding these behaviors is difficult and is typically associated with low reliability across observers. Various difficulties that arise when dealing with prelinguistic vocalizations, especially in the first 6 months of life, are outlined here. A proposed database of digitized infant vocalizations that illustrates strategies used to deal with these difficulties is then described. These strategies are based on theoretical infraphonological constructs, empirical observations, and information about the nature of mature phonological systems. Furthermore, the strategies are open-ended and can be modified as new information becomes available regarding infant vocal behaviors. At present, a preliminary database is available on the Web that illustrates some of these strategies. As the database is expanded, it is expected to provide a general framework for observers to categorize infant vocalizations and thereby enhance observer reliability.