Comparative articulatory modelling of the tongue in speech and feeding

Purpose: Two of the major functions of the human vocal tract are feeding and speaking. As ontogenetically and phylogenetically feeding tasks precede speaking tasks, it has been hypothesised that the skilled movements of the orofacial articulators specific to speech may have evolved from feeding functions. Our objective is to bring evidence to support this hypothesis. Method: Vocal tract articulatory measurements on a male subject have been recorded for speech and feeding by Electromagnetic Articulography. Two linear articulatory models of the jaw/tongue system have been built through statistical analysis for both speech and feeding tasks. Results: The two articulatory models show similar reconstruction accuracy, with 97% and 99% of the variance explained by the five parameters of each model. The speech articulations can be reconstructed from the feeding model with a Root Mean Square error of +0.05 cm from the optimal reconstruction, this error increasing to +0.13 cm for the feeding articulations reconstructed from the speech model. Conclusion: The speech articulations can be reconstructed to a large extent from the feeding movements, the reverse remaining false. It suggests that the speech movements could be considered as a subset of the feeding movements and supports the hypothesis that speech movements may have evolved from feeding movements.