Parameters in the development of Romance perfective auxiliary selection

This paper undertakes a synchronic comparison of auxiliary selection across a number of different Romance varieties that show how minimal differences among otherwise highly homogenous 'systems' can be used to investigate microvariation along the diachronic axis in order to better understand what precisely may vary and how such variation may be implicationally structured in relation to the predictions of parametric hierarchies. Modelling changes in different auxiliary patterns in terms of parametric hierarchies, I argue that the structural organization of such hierarchies and the predictions they make about markedness relations between different linguistic choices can be profitably used, especially when earlier stages of languages are not documented, to understand the direction of change, what precisely may change, and how such diachronic variation may be implicationally structured.