Variability in American English s-retraction suggests a solution to the actuation problem

Abstract Although formulated by Weinreich, Labov, and Herzog in 1968, the actuation problem has remained an unsolved problem in understanding sound change: if sound change is conceived as the accumulation of coarticulation, and coarticulation is widespread, how can some speech communities resist phonetic pressure to change? We present data from American English s-retraction that suggest a partial solution. S-retraction is the phenomenon in which /s/ is realized as an [ʃ]-like sound, especially when it occurs in an /stɹ/ cluster (‘street’ pronounced more like [ʃtɹit] than like [stɹit]). The speech of English speakers judgednotto exhibit s-retraction shows a large coarticulatory bias in the direction of retraction. Further, there is also substantial interspeaker variation in the extent of this bias. We propose that this interspeaker variation, coupled with the coarticulatory bias, facilitates the initiation of sound change. In this account, sound change begins when a listener accidentally interprets an extreme case of a phonetic effect as an articulatory target and then adjusts her own speech in response. This adoption of a new target requires phonetic variation that predates the change. Thus, sound change is predicted to be biased toward phonetic effects that exhibit interspeaker variability, and if sound change requires an accident that is rare, then sound change itself is correctly predicted to be rare as well.