Talker variability and the identification of American English /r/ and /l/ by Japanese subjects

Abstract

Experiments are described that designed to investigate how Japanese subjects develop criteria for ‘‘R’’–‘‘L’’ decisions. Subjects were asked to identify English words beginning with /r/ and /l/ in two conditions: blocked (all words produced by one talker) and mixed (words produced by several talkers). Subjects performed more accurately in the blocked condition than in the mixed condition. This indicates that, as is generally true for native-language perception, stable talker characteristics facilitate non-native speech perception. Subjects also exhibited preferences for ‘‘R’’ or ‘‘L’’ responses for some talkers in one condition, but the opposite or no preference in the other. Together, these results indicate that in the blocked condition, subjects adopted talker-specific criteria. However, when the talker changed randomly in the mixed condition, subjects were not able to adjust their criteria for each talker, but apparently based their criteria upon the range of all /r/s and /l/s they heard. Thus subjects made more responses based on the ‘‘R’’ category for some talkers, and more based on ‘‘L’’ for others. The implications for theories of perceptual normalization and non-native speech perception will be discussed.

Testing the importance of talker variability in non-native speech contrast training

“…When subjects listen to stimuli produced by a single talker, they respond "R" approximately 50% of the time. However, when the same stimuli are mixed with other talkers' productions, rate of "R" response changes significantly for some talkers' productions (Magnuson and Yamada, 1994).…”

Acoustic correlates to the effects of talker variability on the perception of English /r/ and /l/ by Japanese listeners

“…The data we will examine here comes from two previous experiments [2]. In the experiments, we considered the question of whether Japanese listeners are able to adapt to talker-specific differences in cues to /r/ and /l/, or if added variability due to talker differences instead influences sessionspecific criteria, as did the "range" manipulations in [6].…”

“…Second, there were two variations of the blocked condition: the no-break condition was identical to the blocked condition in Experiment 1, but in the break condition, subjects listened to piano music for two minutes between each talker block. This manipulation was used to examine whether subjects were "tuning" to talkers in the blocked condition and whether that tuning persisted over a break (see [2] for details). The subjects were 34 college-age native speakers of Japanese.…”

“…Considering the talker-specific accuracy patterns reported by Lively et al [1] together with the range effects found by Yamada and Tohkura [6] we tested predictions about the effects of within-session talker variability [2]. If Japanese subjects attend mainly to inadequate cues (i.e., non-ecologically valid cues), one might predict that to naive Japanese listeners, the relative range of cues to /r/ and /l/ would increase when stimuli from two or more talkers are presented within a block as compared to when stimuli from only one talker are presented within a block.…”

“…However, these effects are not well-understood, as acoustic correlates to the effects have proven difficult to establish. We report analyses of subject differences and acoustic measurements which may help to describe the acoustic phenomena underlying one class of talker effects that we have reported previously; specifically, the interaction of talker and talker condition (the number of talkers heard within a block of trials --one or several) [2]. Correlations between response measures and acoustic measures suggest that when stimuli from several talkers are mixed randomly in a block of trials, subjects without well-formed categories for /r/ and /l/ attempt to use the duration of the initial steady-state portion of an /r/ or /l/ stimulus (an unreliable cue) for categorization, whereas native speakers use F3 [6].…”