The ethologic model of phonetic development: 111. The phonetic product

The ethologic model of phonetic development supposes that the increased use of different places of consonant-like (closant) and vowel-like (vocant) articulation defines the growth of phonetic diversity early in life (Bauer, 1988b). To test this model, vocalizations were sampled from children during caregiver-child play interactions. It was hypothesized that regular development of phonetic diversity could be defined by applying a measure, the phonetic product (PP) estimator, to the vocalizations of two groups of infants (referred to as the Omaha and Syracuse groups). The Omaha group of five children were sampled at 13 and 24 months of age, while the Syracuse group of six children were sampled monthly between 8 and 25 months of age. Phonetic diversity was estimated for each vocalization using the weighted PP of counted phones in eight different phonetic categories. The PP increased between the two sampling ages for the Omaha group and had a monthly growth for the Syracuse group. These findings, relating the PP to age, support the hypothesis that phonetic diversity increases as predicted by the ethologic model of phonetic development.