Specificity and generalizability of spontaneous phonetic imitation

The imitation paradigm [1, 2], in which subjects' speech is compared before and after they are exposed to target speech, has shown that subjects shift their production in the direction of the target, indicating the use of episodic traces in speech perception as well as the close tie between speech perception and production. By using this paradigm, the current study aims to investigate the psychological reality of three levels of linguistic unit (i.e., word, phoneme, and feature). An experiment was designed to test whether spontaneous phonetic imitation can be generalized from words across (a) new words which share the same initial phoneme, and (b) new words with a new phoneme falling in the same natural class (sharing a feature); and also whether word-level specificity can be obtained through physical measurements instead of perceptual assessments. The feature manipulated in the experiment was aspiration, or [+spread glottis], on the phonemes /p/ and /k/. The results showed that subjects produced significantly longer VOTs after they were exposed to target speech with longer VOTs, replicating [2] in a non-shadowing paradigm. Furthermore, the modeled feature (increased aspiration) was generalized to new instances of /p/ (i.e., in new words) as well as to the new segment /k/. At the same time, subjects’ post-exposure VOT was significantly longer for those items that were in the target speech than items which they had not previously heard. These results, taken together, indicate that speakers possess both sub-phonemic and wordlevel representations.