Cross-dialect speech perception as a locus for sound change
Speech is characterized by substantial acoustic-phonetic variability that conveys both linguistic information about the intended message as well as indexical information about the talker. Although speech perception is typically robust to this variability, indexical information can interfere with linguistic processing in difficult listening conditions. This interference is reduced when the indexical sources of variability are familiar, such as familiar talkers or foreign accents. Linguistic information is also perceived more quickly and accurately when it is produced in a familiar dialect, such as the local or standard variety, than when it is produced in a less familiar dialect. These familiarity effects suggest that linguistic and indexical information are integrated in language processing. This integration of linguistic and indexical information provides a potential locus for sound change in cross-dialect speech perception when listeners are confronted with different dialect-specific variants from a single linguistic category. In particular, listeners who are familiar with multiple different dialects exhibit both processing costs and benefits in cross-dialect speech perception involving familiar dialects. Processing benefits have been observed in intelligibility and semantic priming tasks, whereas processing costs have been observed in lexical classification and form priming tasks. This complex profile of costs and benefits reflects the competition between potential form-meaning mappings that results from overlapping phonological representations of multiple dialect-specific variants within an individual listener. These overlapping representations are inherently less stable than the more uniform representations of listeners with primary exposure to only a single variety and may therefore be subject to change over time. This potential for change can contribute to both dialect leveling, when the standard dialect representations outweigh the local dialect representations, and dialect divergence, when the local dialect representations are deflected away from competing standard variants.