PhD Student Miroo Lee presents "The Locus of Language Mode Effects in Speech Perception"

The Locus of Language Mode Effects in Speech Perception

Previous research suggests bilingual listeners’ sound perception can be affected by language mode (Bürki-Cohen, Grosjean, & Miller, 1989; Elman, Diehl, & Buchwald, 1977; Grosjean, 1997). Most studies have employed a labeling task and found a shift in phonemic boundaries in different language modes. However, labeling involves decision making at a higher level. As a result, the task doesn’t necessarily inform us as to the actual perception process happening at a lower level. The current study aims to bridge this gap by using a discrimination task in addition to a labeling task. The current study asks, (1) whether language mode affects acoustic sensitivity, (2) at which processing levels do the language mode effects arise. We tested Korean-English bilinguals’ sensitivity to pitch (F0) during perception of both meaningless syllables and real words. In English, F0 is a secondary cue to stop consonant voicing (with VOT as the primary cue, e.g., for the contrast between /pa/ and /ba/), but Korean relies on both VOT and F0 (Cho, Jun, & Ladefoged, 2002).

An F0 continuum from 200 to 260 Hz was created by manipulating a naturally produced [pa] sound. Participants (n=22 late bilinguals; n=10 monolinguals) completed three listening tasks: a labeling task ("Is this sound [ba] or [pa]?"), a syllable discrimination task ("Are these sounds the same or different?"), and a word discrimination task ("Are these words the same or different?"). Language mode was manipulated across two separate days: both groups completed an English session followed by a Korean session. Critically, the same continua were used throughout (with different rhymes appended), so any differences across tasks must be attributed to some aspect of the listening mode. The labeling responses, d’, and the false alarm rate were analyzed to test the effects of mode (“English”, “Korean”) and category (“ba”,”across”,”pa”).

The results indicate different effects of language mode in bilinguals’ and monolinguals’ perception. As for the labeling task, monolinguals did not show any changes in their response as a function of F0, consistently labeling the entire F0 continuum as voiceless sound. As for bilinguals, their responses indicated effects of F0 as the low F0 was labeled as English voiced and Korean lenis, whereas high F0 was labeled as English voiceless and Korean aspirated. As for the discrimination tasks, both speaker groups showed sensitivity to category, which was expected for bilingual speakers but surprising for monolingual speakers. The combined results of d’ and the false alarm rate suggest that language mode has effects on a decision factor for bilingual speakers, while language mode has effects on a sensory factor for monolingual speakers.

 

Key words: language mode, F0 categorical perception, speech perception, adult language learners, acoustic cue sensitivity, false alarm