VOCAL COMMUNICATION IN THE 1ST 18 MONTHS OF LIFE

Fifty-one normally developing infants aged birth to 18 months, 10 or 1 1 in each of five age groups, were videorecorded in their homes before and after an expected change in the form of their vocalizations and u nder a set of conditions that reflected common daily occurrences. The vocalizations produced were coded according to their communicative con texts, defined in nonvocal behavioral terms. Communicative codes were assigned to seven major categories. The distribution of codes across c ategories was found to be different for different age groups. It varie d between the first and second observations; however, the pattern of c hange differed across age groups. Data from individuals were transform ed to proportions, to control for individual differences in productivi ty. They were then found to reflect differences in level of developmen t of vocal communication. It was concluded that vocal communication fo llows an orderly developmental sequence in normally developing infants in the first 18 months of life.