“…Speech categories are highly multidimensional, with dimensions that are difficult to describe verbally and are often perceptually integral (Francis et al, 2000;Grau & Kemler Nelson, 1988;Hillenbrand et al, 1995). Further, the physical constraints on articulatory mechanisms mean that the various acoustic input dimensions across which speech sounds can vary are not necessarily independent (Carré, 2009;Diehl, 2008;Kingston, Diehl, Kirk, & Castleman, 2008;Macmillan, Kingston, Thorburn, Walsh Dickey, & Bartels, 1999). As a result, there are likely to be interdependencies that would result in the kind of 'natural covariation' that we posit might explain the relationship between CF and MF in the current study.…”