Individual differences in phonetic cue use in production and perception of a non-native sound contrast

Abstract

The current work examines native Korean speakers’ perception and production of stop contrasts in their native language (L1, Korean) and second language (L2, English), focusing on three acoustic dimensions that are all used, albeit to different extents, in both languages: voice onset time (VOT), f0 at vowel onset, and closure duration. Participants used all three cues to distinguish the L1 Korean three-way stop distinction in both production and perception. Speakers’ productions of the L2 English contrasts were reliably distinguished using both VOT and f0 (even though f0 is only a very weak cue to the English contrast), and, to a lesser extent, closure duration. In contrast to the relative homogeneity of the L2 productions, group patterns on a forced-choice perception task were less clear-cut, due to considerable individual differences in perceptual categorization strategies, with listeners using either primarily VOT duration, primarily f0, or both dimensions equally to distinguish the L2 English contrast. Differences in perception, which were stable across experimental sessions, were not predicted by individual variation in production patterns. This work suggests that reliance on multiple cues in representation of a phonetic contrast can form the basis for distinct individual cue-weighting strategies in phonetic categorization.

Individual differences in perceptual adaptability of foreign sound categories

“…In previous work (Schertz et al, 2015), we found substantial variability in native Korean listeners’ cue weighting strategies in distinguishing their L2 English stop contrast: while some Korean listeners used primarily VOT to distinguish the contrast in a forced-choice task, like native English listeners do, most either used primarily f0, or made use of both dimensions (requiring both long VOT and high f0 to categorize stimuli as voiceless /p/). This tendency to rely on f0 likely stems from the fact that the three-way stop contrast in Korean relies heavily on both VOT and f0 (e.g.…”

“…Cho et al, 2002; Lee and Jongman, 2012). Interestingly, Korean speakers vary both VOT and f0 to an equal extent when distinguishing their L2 English stop contrast in production (Schertz et al, 2015), but this cue use is not necessarily reflected in their perception . The factors underlying these differences in phonetic structure are not yet known; however, recent work by Kong and Yoon (2013) suggests that listeners’ level of English proficiency plays a role, with higher-proficiency speakers using f0 less (i.e.…”

“…Based on Korean perception data reported in Schertz et al (2015), we expected individual Korean listeners to use different strategies for distinguishing the contrast, with some relying primarily on VOT, some relying primarily on f0, and some relying on the two dimensions to a similar extent. If the same processes drive adaptation in non-native sound categories, regardless of which dimension is dominant, then we would expect different (but symmetrical) patterns of adaptation for the Korean listeners, with the specific pattern determined by these initial individual categorization patterns.…”

“…Although recent work suggests that L2 listeners show lexically-guided phonetic tuning (Reinisch et al, 2013), this has only been shown for phonetic categories which are virtually identical across the two languages. Furthermore, although we expect most Korean listeners to rely on f0 more than VOT for the English contrast, VOT may still play a significant role, given that VOT is the most reliable indicator of English stop category membership in Koreans’ productions of their L2 English contrast (Schertz et al, 2015). …”

Flexible and adaptive processes in speech perception

“…Exposure to changes in the dimensional relationship between two properties of speech leads to changes in perception (dimension-based statistical learning) but only if the manipulation did not violate typical learned long-term relationship regularity between the two dimensions (e. g., Idemaru & Holt, 2011). Recent examples show that changes in perception are sensitive to specific languages (Schertz, 2014), individual biases (Schertz, Lotto & Warner, 2015), and to linguistic experience (Cooper, 2016). What is the basis for these differences?…”