This article explores intraindividual microvariation in dialect syntax. We argue that in many cases the speaker has internalized a different (sub)grammar for each dialectal variety, in line with the hypothesis of universal bilingualism and parallel grammars argued for by Roeper (1999 et seq.). We discuss the question of how we can distinguish parallel grammars from optionality within one grammar, suggesting that the identification of correlating contextual factors might be a promising criterion. However, we also explore a more subtle type of variation, namely cases where a standard variety influences a potentially more vulnerable non-standard variety in a way that makes it exceedingly difficult for the language user and even for a trained linguist to discern what is what. We discuss whether or not these properties should be analysed as properties of another subgrammar (the standard grammar) or as fully integrated (albeit acquired) properties of the non-standard dialect.
