研究者詳細 - 石田　真子

石田　真子（イシダ　マコ）

Ishida, Mako

写真a

所属（所属キャンパス）: 理工学部外国語・総合教育教室（日吉）

職名: 専任講師

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Perceptual restoration of locally time-reversed speech: Non-native listeners’ performance in their L2 vs. L1

Ishida M.

Attention, Perception, and Psychophysics （Attention, Perception, and Psychophysics） 2021年

ISSN 19433921

　概要を見る

Nonnative listeners are generally not as good as native listeners in perceptually restoring degraded speech and understand what was being said. The current study investigates how nonnative listeners of English (namely, native Japanese speakers who learned English as a second language) perceptually restore temporally distorted speech in their L2 English as compared with native English listeners (L1 English) reported in Ishida et al. (Cognition, 151, 68–75, 2016), and as compared with the listeners’ native tongue (L1 Japanese). In the experiment, listeners listened to locally time-reversed words and pseudowords in their L2 English and L1 Japanese where every 10, 30, 50, 70, 90, or 110 ms of speech signal was flipped in time—these stimuli contained either many fricatives or stops. The results suggested that the intelligibility of locally time-reversed words and pseudowords deteriorated as the length of reversed segments increased in both listeners’ L2 English and L1 Japanese, while listeners understood locally time-reversed speech more in their L1 Japanese. In addition, lexical context supported perceptual restoration in both listeners’ L1 Japanese and L2 English, while phonemic constituents affected perceptual restoration significantly only in listeners’ L1. On the other hand, locally time-reversed words and pseudowords in L1 Japanese were much more intelligible than those in L1 English reported in Ishida et al. It is possible that the intelligibility of temporally distorted lexical items depends on the structure of basic linguistic units in each language, and the Japanese language might have a unique characteristic because of its CV and V structure.
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Perceptual restoration of temporally distorted speech in L1 vs. L2: Local time reversal and modulation filtering

Ishida M., Arai T., Kashino M.

Frontiers in Psychology （Frontiers in Psychology） 9 （ SEP ） 2018年09月

　概要を見る

Speech is intelligible even when the temporal envelope of speech is distorted. The current study investigates how native and non-native speakers perceptually restore temporally distorted speech. Participants were native English speakers (NS), and native Japanese speakers who spoke English as a second language (NNS). In Experiment 1, participants listened to "locally time-reversed speech" where every x-ms of speech signal was reversed on the temporal axis. Here, the local time reversal shifted the constituents of the speech signal forward or backward from the original position, and the amplitude envelope of speech was altered as a function of reversed segment length. In Experiment 2, participants listened to "modulation-filtered speech" where the modulation frequency components of speech were low-pass filtered at a particular cut-off frequency. Here, the temporal envelope of speech was altered as a function of cut-off frequency. The results suggest that speech becomes gradually unintelligible as the length of reversed segments increases (Experiment 1), and as a lower cut-off frequency is imposed (Experiment 2). Both experiments exhibit the equivalent level of speech intelligibility across six levels of degradation for native and non-native speakers respectively, which poses a question whether the regular occurrence of local time reversal can be discussed in the modulation frequency domain, by simply converting the length of reversed segments (ms) into frequency (Hz).
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Simultaneous articulatory and acoustic distortion in L1 and L2 Listening: Locally time-reversed "fast" speech

Ishida M.

Proceedings of the Annual Conference of the International Speech Communication Association, INTERSPEECH （Proceedings of the Annual Conference of the International Speech Communication Association, INTERSPEECH） 2017-August 571 - 575 2017年

ISSN 2308457X

　概要を見る

The current study explores how native and non-native speakers cope with simultaneous articulatory and acoustic distortion in speech perception. The articulatory distortion was generated by asking a speaker to articulate target speech as fast as possible (fast speech). The acoustic distortion was created by dividing speech signals into small segments with equal time duration (e.g., 50 ms) from the onset of speech, and flipping every segment on a temporal axis, and putting them back together (locally time-reversed speech). This study explored how "locally time-reversed fast speech" was intelligible as compared to "locally time-reversed normal speech" measured in Ishida, Samuel, and Arai (2016). Participants were native English speakers and native Japanese speakers who spoke English as a second language. They listened to English words and pseudowords that contained a lot of stop consonants. These items were spoken fast and locally time-reversed at every 10, 20, 30, 40, 50, or 60 ms. In general, "locally time-reversed fast speech" became gradually unintelligible as the length of reversed segments increased. Native speakers generally understood locally time-reversed fast spoken words well but not pseudowords, while non-native speakers hardly understood both words and pseudowords. Language proficiency strongly supported the perceptual restoration of locally time-reversed fast speech.
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Missing phonemes are perceptually restored but differently by native and non-native listeners

Ishida M., Arai T.

SpringerPlus （SpringerPlus） 5 （ 1 ） 2016年12月

　概要を見る

This study investigates how similarly present and absent English phonemes behind noise are perceived by native and non-native speakers. Participants were English native speakers and Japanese native speakers who spoke English as a second language. They listened to English words and non-words in which a phoneme was covered by noise (added; phoneme + noise) or replaced by noise (replaced; noise only). The target phoneme was either a nasal (/m/ and /n/) or a liquid (/l/ and /r/). In experiment, participants listened to a pair of a word (or non-word) with noise (added or replaced) and a word (or non-word) without noise (original) in a row, and evaluated the similarity of the two on an eight-point scale (8: very similar, 1: not similar). The results suggested that both native and non-native speakers perceived the ‘added’ phoneme more similar to the original sound than the ‘replaced’ phoneme to the original sound. In addition, both native and non-native speakers restored missing nasals more than missing liquids. In general, a replaced phoneme was better restored in words than non-words by native speakers, but equally restored by non-native speakers. It seems that bottom-up acoustic cues and top-down lexical cues are adopted differently in the phonemic restoration of native and non-native speakers.
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Some people are "More Lexical" than others

Ishida M., Samuel A.G., Arai T.

Cognition （Cognition） 151 68 - 75 2016年06月

ISSN 00100277

　概要を見る

People can understand speech under poor conditions, even when successive pieces of the waveform are flipped in time. Using a new method to measure perception of such stimuli, we show that words with sounds based on rapid spectral changes (stop consonants) are much more impaired by reversing speech segments than words with fewer such sounds, and that words are much more resistant to disruption than pseudowords. We then demonstrate that this lexical advantage is more characteristic of some people than others. Participants listened to speech that was degraded in two very different ways, and we measured each person's reliance on lexical support for each task. Listeners who relied on the lexicon for help in perceiving one kind of degraded speech also relied on the lexicon when dealing with a quite different kind of degraded speech. Thus, people differ in their relative reliance on the speech signal versus their pre-existing knowledge.
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