Asymmetries in vowel perception, in the context of the Dispersion-Focalisation Theory

In a recent paper in this journal, Polka and Bohn [Polka, L., Bohn, O.-S., 2003. Asymmetries in vowel perception. Speech Communication 41, 221-231] display a robust asymmetry effect in vowel discrimination, present in infants as well as adults. They interpret this effect as a preference for peripheral vowels, providing an anchor for comparison. We discuss their data in the framework of the Dispersion-Focalisation Theory of vowel systems. We show that focalisation, that is the convergence between two consecutive formants in a vowel spectrum, is likely to provide the ground for anchor vowels, by increasing their perceptual salience. This enables to explain why [y] is an anchor vowel, as well as [i], [a] or [u]. Furthermore, we relate the asymmetry data to an old experiment we had done on the discrimination of focal vs. non-focal vowels. Altogether, it appears that focal vowels, more salient in perception, provide both a stable percept and a reference for comparison and categorisation.