2009/03/26

Mann, V. A, & Bruno H. R. (1980). Influence of vocalic context on perception of the [ʃ]-[s] distinction. Perception & Psychophysics, 28(3), 213–228.

Presentation: Sarah

Summary: Shelly

Previous investigations have found that the roundedness of the following vowels would influence listeners’ perception of [ʃ] and [s].Given the same fricative noise, listeners perceive more instances of [s] when it is followed by [u] than by [a]. This phenomenon was explained by the hypothesis that our perception on syllable-initial consonants would be adjusted due to our knowledge of the coarticulation effect from speech production experiences. The purpose of the present study is to test this hypothesis. In the first experiment the authors tried to replicate the findings of previous studies. Five conditions were designed for testing: (1) isolated long noise, (2) short noise immediately followed by [ta] or [tu] ([t] is the synthesized transition), (3) short noise followed by a 150-ms silence and either [ta] or [tu], and (4) long noise followed by a 150-ms silence and either [ta] or [tu]. Subjects needed to answer whether they heard a [s] or [ʃ] as the initial consonant. The results showed that indeed more responses of [s] were elicited when the following vowel is [u], and such effect would be nearly eliminated when a gap was introduced between the consonant and vowel. Experiment 2 aimed to further examine whether temporal separation between the noise and the following vowels would diminish the effect from vowels. By introducing 8 gap durations: 0, 10, 20, 30, 40, 50, 100, and 150 ms, and asking subjects whether they hear “s”, “sh”, “st”, “sk”, “sht”, or “shk”, the results showed that when gaps were introduced, more subjects heard the stops, but the effect of vowel still existed, which suggested that either the transition in the vowel or the vowel itself has influenced listener’s perception. In Experiment 3, stimuli with and without transition were tested to check whether the vowel effect found in the previous experiments was actually the effect from transition. Results showed that the vowel effect disappeared transition was excluded, which strongly suggested that transition is the source of the effect, not the vowel. However, there is a possibility that the vowel is still the source of effect, while transition is just a medium between the noise and the following vowel, and without the medium, the vowel effect will fail to influence the perception of the noise. To test this possibility, a fourth experiment was conducted. By using the transition and vowel from the [ʃa], [ʃu], [sa], and [su] of real utterances, the authors aimed to test whether the information of places of articulation of [ʃ] and [s] carried by transition would influence the result of perception. If they do, we can then conclude that transition is the source of effect, and if they do not, then we can attribute the effect to the following vowels. Results showed that both transition and vowel were effective. Though the results from the above experiments cannot be explained with a single hypothesis, one could be surer that our experience from speech production would indeed influence our speech perception.