Variation within grammars is a reflection of variation between grammars. Subject agreement and synthetic negation for the verb be show extraordinary local variation in the Survey of English Dialects (Orton et al., 1962–71). Extracting partial grammars of individuals, we confirm leveling patterns across person, number, and negation (Ihalainen, 1991; Cheshire, Edwards & Whittle, 1993; Cheshire, 1996). We find that individual variation bears striking structural resemblances to invariant dialect paradigms, and also reflects typologically observed markedness properties (Aissen, 1999). In the framework of Stochastic Optimality Theory (Boersma & Hayes, 2001), variable outputs of individual speakers are expected to be constrained by the same typological and markedness generalizations found crosslinguistically. The stochastic evaluation of candidate outputs in individual grammars reranks individual constraints by perturbing their ranking values, with the potential for stable variation between two near-identical rankings. The stochastic learning mechanism is sensitive to variable frequencies encountered in the linguistic environment, whether in geographical or social space. 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 paradigms. A characteristic of linguistic variation that has emerged in distinct fields of enquiry is that variation within a single grammar bears a close resemblance to variation across grammars. Sociolinguistic studies, for instance, have long observed that ‘variation within the speech of a single speaker derives from the variation which exists between speakers’ (Bell, 1984: 151). In the present study, individual patterns of variation in subject–verb agreement with affirmative and negative be extracted from the Survey of English Dialects(SED, Orton et al., 1962–71) show striking structural resemblances to patterns of interdialectal, or categorical, variation.