Unequal effects of speech and nonspeech contexts on the perceptual normalization of Cantonese level tones

Abstract

Context is important for recovering language information from talker-induced variability in acoustic signals. In tone perception, previous studies reported similar effects of speech and nonspeech contexts in Mandarin, supporting a general perceptual mechanism underlying tone normalization. However, no supportive evidence was obtained in Cantonese, also a tone language. Moreover, no study has compared speech and nonspeech contexts in the multi-talker condition, which is essential for exploring the normalization mechanism of inter-talker variability in speaking F0. The other question is whether a talker's full F0 range and mean F0 equally facilitate normalization. To answer these questions, this study examines the effects of four context conditions (speech/nonspeech × F0 contour/mean F0) in the multi-talker condition in Cantonese. Results show that raising and lowering the F0 of speech contexts change the perception of identical stimuli from mid level tone to low and high level tone, whereas nonspeech contexts only mildly increase the identification preference. It supports the speech-specific mechanism of tone normalization. Moreover, speech context with flattened F0 trajectory, which neutralizes cues of a talker's full F0 range, fails to facilitate normalization in some conditions, implying that a talker's mean F0 is less efficient for minimizing talker-induced lexical ambiguity in tone perception.

Toward an integrative model of talker normalization.

“…Moreover, the perceptual performance was influenced by talker typicality in F0 range, despite the contextual F0 cues. This indicates that general contrast of auditory cues may not be sufficient for talker normalization in the perception of Cantonese level tones, which is consistent with the findings of previous studies (Chen & Peng, 2015;Francis et al, 2006;Zhang et al, 2012;Sjerps et al, 2012).…”

“…In two studies, Zhang et al (2012Zhang et al ( , 2013 further confirmed that the effects of speech and nonspeech context were unequal on the perception of Cantonese level tones, with a more careful design of the nonspeech context (using a triangle wave to generate the nonspeech context). The findings of Francis et al (2006) were largely replicated.…”

“…There is plenty of evidence that listeners estimate the location/identity of a lexical tone according to the distribution of a talker's speaking F0 in a speech context (Chen & Peng, 2015;Francis, Ciocca, Wong, Leung, & Chu, 2006;Huang & Holt, 2009;Leather, 1983;Lin & Wang, 1984;Moore & Jongman, 1997;Wong & Diehl, 2003;Zhang et al, 2012Zhang et al, , 2013. Lin and Wang (1984) investigated how the relative F0 height of a single-word context affected the perception of Mandarin tones.…”

Context Effect in the Categorical Perception of Mandarin Tones

“…Studies [3][4][5] have clearly demonstrated that the perception of Cantonese level tones is context-dependent. Francis et al [3] found that target stimuli were also more likely to be perceived as low-level tones when positioned in a synthesized context with high F0, whereas the same set of stimuli were perceived as high-level tones in a synthesized context with low F0.…”

“…As for word-external cues, they mainly refer to acoustic cues in the context, and are thus also known as Bcontextual cues^. Often, listeners make use of both word-internal F0 cues and contextual F0 cues for tone normalization [3][4][5][6]. But on some occasions, contextual cues with information about a talker's F0 range can be more crucial, such as when the stimuli to be categorized are highly ambiguous because they are located close to the perceptual boundaries of two tones.…”