Summary
A series of attempts to develop a behavioural classification system for use in a first stage analysis of infant vocalization data are reported. The data were cross-sectional and obtained from 11 different infants between the ages of 1 and 40 weeks. A set of terms and definitions were developed by two judges and their reliability assessed by having a third judge classify the data, using the terms and definitions in written form only. Implifications of the findings with respect to inter-judge agreement and disagreement and usefulness of system for further studies of infant vocalization are discussed.