|Abstract:||Subject agreement and synthetic negation for the verb ‘be’ show extraordinary local variation in the Survey of English Dialects (SED, Orton et al. 1962-71). Extracting partial grammars of individuals, we confirm leveling patterns across person, number, and negation (Ihalainen 1991; Cheshire, Edwards, and Whittle 1993; Cheshire 1996). We find that individual alternations of forms bear striking structural resemblances to invariant dialect paradigms, and also reflect typologically observed markedness properties (Aissen 1999). In the framework of stochastic Optimality Theory (Boersma and Hayes 2001), variable outputs of individual speakers are expected to be constrained by the same kinds of typological and markedness generalizations that are found cross-linguistically. The stochastic evaluation of candidate outputs in individual grammars reranks constraints by perturbing their ranking values, often matching the individual grammar to variable frequencies encountered in the linguistic environment. As a result, individual variation samples the typological space of possible grammars and reflects features of categorical grammars it comes into contact with. In addition to relating individual and group dialectal variation to typological variation (Kortmann 1999; Anderwald 2003), the findings suggest that an individual grammar is sensitively tuned to frequencies in the linguistic environment, leading to isolated loci of variability in the grammar rather than complete alternations of forms as in a competing grammars model.