The Pairwise Variability Index and coexisting rhythms in language

The Pairwise Variability Index (PVI) has been widely used as a metric for quantifying rhythm in languages, often with a view to placing them on a continuum between notional categories of stress-timing and syllable-timing. We review the history of and rationale for the PVI, and point out three potential anomalies in the way the PVI has been applied. Following up one of these we apply the PVI to the level of the foot, and argue that stress-timing and syllable-timing are not points at either end of a continuum but orthogonal dimensions, so that a language can be (for instance) both syllable-timed and stress-timed. Results from Estonian, English, Mexican Spanish, and Castilian Spanish are presented which give some support for this view.