Factor analysis of tongue shapes

A new analytic procedure PARAFAC has been applied to the description of the shape of the tongue in English vowels. The procedure models the data in terms of a unique set of possibly explanatory factors. It solves in parallel for factors in several data sets, simultaneously describing the differences among data sets in terms of different relative involvement of these common factors. Tracings were made of x-rays taken during the pronunciation of 10 English vowels by five speakers. The positions of the tongue in these 50 vowels were quantized in terms of 13 superimposed grid lines. PARAFAC analysis shows that the data can be described in terms of two factors. One factor generates a forward movement of the root of the tongue accompanied by an upward movement of the front of the tongue. The second factor generates an upward and backward movement of the tongue. Movements from front to back vowels involve decreasing amounts of factor one. Movements from high to low vowels involve decreasing amounts of factor two. Different speakers use the two factors to different degrees which may be associated with their individual anatomy. The correlation between the observed data and that predicted by the model is greater than 0.96.