The emergence of phonetic-phonological features in a biologically inspired model of speech processing

Because speech acquisition begins with sensorimotor activity (i.e. babbling and imitation of speech items in order to learn articulatory-acoustic relations) as well as with semantic cognitive processing (i.e. linking phonetic items with concepts), distinctiveness as well as phonetic-phonological features emerge early in speech acquisition. Based on a biologically inspired model of speech processing, using interconnected growing self-organizing maps (I-GSOMs), the phonetic-phonological interface is described here in terms of a numerical computer-implemented model. By simulating early phases of speech acquisition, it can be shown that vocalic features like low-high as well as consonantal features describing the manner of articulation (like plosive, fricative, nasal, lateral, etc.) already arise at sensorimotor levels. This is reflected in our model by an ordering of syllables with respect to phonetic-phonological features at the level of an auditory based neural map. Other features like consonantal place of articulation (labial, apical, dorsal) as well as voiced-voiceless emerge at higher levels within our model, i.e. at the level of neural associations between a phonetic and a semantic neural map. It can be hypothesized from these findings that the phonetic-phonological interface does not appear as a clean cut within the speech processing system but as a broader zone within that system located between sensorimotor and semantic processing.