Speech perception is highly robust to variation, but familiarity with a particular source of variation can nevertheless lead to significant processing benefits. In the domain of cross-dialect speech perception, familiar local and standard varieties have been shown to facilitate lexical and semantic processing relative to unfamiliar dialects. However, more recent research suggests that individuals with exposure to both a local non-standard variety and a regional or national standard variety exhibit a mix of lexical processing costs and benefits, suggesting that familiarity with multiple different linguistic systems can result in both independent processing benefits for each variety as well as competition among variable multi-dialect representations. In an exemplar model of language processing, this complex pattern of results suggests several loci for sound change within an individual language user. Although the processing benefits associated with the local variety may contribute to long-term maintenance of variation through divergence from a regional or national standard, the processing benefits associated with the standard may contribute to dialect leveling and convergence towards the standard. Competition between these forces for maintenance and leveling will be observed most strongly in individuals with extensive exposure to both a non-standard local variety and a regional or national standard.