31. A method of assessing a key child's expressive language development, comprising: processing an audio recording taken in the key child's language environment to identify segments of the recording that correspond to the key child's vocalizations; applying an adult automatic speech recognition phone decoder to segments of the key child's vocalizations to identify each occurrence of each of a plurality of phone categories, wherein each of the phone categories corresponds to a pre-defined speech sound, wherein applying an adult automatic speech recognition phone decoder comprises identifying occurrences of a plurality of non-phone categories, wherein each of the non-phone categories corresponds to a pre-defined non-speech sound; determining a distribution for the phone categories; and using the distribution in an age-based model to assess the key child's expressive language development.
32. The method of claim 31 , wherein the pre-defined non-speech sounds include vocalizations, cries, vegetative sounds, and fixed sounds.