Samuel, A. 1, 2, 4 & Kraljic, T. 3
1 Basque Center on Cognition, Brain, and Language
2 Stony Brook University
3 University of Pennsylvania, Nuance communications
4 Ikerbasque, Basque Foundation for Science
The perceptual system’s two main requirements are potentially conflicting: It should be as stable as possible, but it should also adjust to a changing environment. A growing body of research is clarifying how the system balances these requirements in the perception of speech. Many studies have shown that when a listener receives an ambiguous phonetic input, additional context (e.g., lexical; visual ) is used both to resolve the phonetic ambiguity in the moment, and to adjust the associated perceptual representation that informs subsequent perception. For example, if the /s/ in “Tennessee” is produced with a somewhat “sh”-like quality, the lexical context both determines that the segment was /s/, and expands the /s/ category for later inputs. Kraljic, Brennan, & Samuel (2008) tested a possible constraint on this adjustment process by exposing listeners to these ambiguous segments, but only in a particular context: /str/ (as in “abstract”, or “district”). In the participants’ local dialect of American English, /s/ before /tr/ is typically produced as precisely such an ambiguous sound. The theoretical question was whether perceptual adjustment would occur under these circumstances. It did not. Thus, the same ambiguous segments that reliably generate retuning in other contexts do not do so in the /str/ context, implicating an additional factor. Kraljic et al. discussed the possibility that a dialectal “explanation” for phonetic ambiguity might block the adjustment process. However, they noted that the shift in /s/ before /tr/ is also a form of place assimilation. Thus, the blocking of adjustment could either be due to dialect, or to assimilation. In the current work, we tease these two cases apart, testing a case of dialect without assimilation, and a case of assimilation without dialect. The results favor blocking based on assimilation, rather than dialect, clarifying the processing levels that are subject to perceptual adjustment.