Epenthetic vowels in Japanese: a perceptual illusion? Emmanual Dupoux, et al (1999) By Carl O’Toole

Question: To what extent do phonotactics, language specific constraints on phonemes, play a role in speech perception?

Problem All of the studies have been conducted within a single language.

Background  Japanese add epenthetic [u] or [o] after every syllable final C  Fight  Faito  Sphinx  SufiNkusu

Purpose Explore the role of phonotactics on perception by investigating the perceptual reality of epenthesis using offline phoneme detection tasks (experiments 1 and 2) and through 2 speeded ABX tasks (experiments 3 and 4).

Experiment 1: Epenthesis  asked to listen to stimuli spoken by a Japanese speaker through headphones  participant were asked to indicate if they hear an [u] in the middle of the stimuli  Stimuli ‘ebzo’ and ‘ebuzo’.

Method  Given 10 sequences of the type VC 1 uC 2 V, C1 is a voiced or voiceless stop; C2 is a nasal or obstruent;V is any Japanese vowel that is not [u].  6 sets where the length of the vowel went from 0 ms to 18 to 36 to 54 to 72 to 89 ms (full vowel length )

Results Experiment 1

Problem The speaker that the participants listened to was Japanese. Although the segments had been edited to remove the [u], there could have been co-articulatory cues remaining that would have ‘told’ the Japanese participants to expect an [u].

Solution  Experiment 2  Repeat experiment #1 almost exactly but exchange the Japanese speaker with a French one  2 extra conditions: –1) make ‘ebzo’ with absolutely NO [u] sound –2) add a new vowel [i]to the CC cluster to the ‘ebizo’ to measure baseline performance

Results Experiment 2

Figures 1 and 2

Problem There are no controls for metalinguistic judgment. Participants had to know what a vowel is in order to do the experiments. Since the writing systems of Japanese and French are different, it is possible that the writing systems could affect vowel judgments in Japanese and French participants.

Solution  Experiment 3  ABX identity judgment tasks.  hear 3 stimuli in a row decide if the 3 rd stimulus matches the 1 st or the 2 nd.  responses timed to reduce likelihood of complicated response strategies.

Purpose:  1) test perceptual basis of experiments 1 and 2.  2) test whether listeners impose their native phonology on unfamiliar linguistic stimuli regardless of whether the stimuli was foreign or native.

Method  speaker of the X sequence different from the A and B sequences.  crossover experiment introduced where contrastive vowel length also tested ‘ebuuzo’ vs. ‘ebuzo’  Stimuli were presented at a rate of 500 ms per sequence with 4 seconds for the participant to respond.

Method cont…  next set started 1 second after the response or after 5 seconds depending on whether a judgment was made or not.  The lengths of the vowel difference were 95 ms in the ‘ebuuzo’- ‘ebuzo’ case and 89 ms in the ‘ebzo’ – ‘ebuzo’ case

Results Experiment 3

Problem Introducing a change in speaker to reduce low-level acoustic characteristics and increase reliance on abstract phonological representation was a deviation from the scientific norm. Will the results hold if there is no speaker change and the participants can rely on purely acoustic information?

Solution  Experiment #4  designed to be the same as #3 but with some additional changes.  the speaker would remain the same through out the sets and that X would be acoustically identical to either A or B.

Added Purposes Examine the epenthesis effect by: –1)examining the effect of practice, –2) checking the influence of experience with foreign languages by the participants.

Methods:  participant selection, materials and experimental procedures were the same as in experiment #3.  biographical questionnaire about foreign language experiences  participants evaluated subjectively by native French or English speakers  participants categorized in relation to their ability.

Results Experiment 4

Tables 1 and 2

Results  Japanese participants perceived an [u] between consonant clusters regardless of whether there was one there or not. They could however clearly tell the difference between 1 or 2 [u] vowels in a row.  French participants were quite capable of perceiving when an [u] was present between clusters and when it wasn’t but they had considerable trouble identifying 1 vs 2 [u] vowels in a row.

Results cont …  Practice reduced response times and error rates but did not change the size of the effect nor did ability in CC languages seem to make much of a difference for the Japanese participants

Findings Overall these findings indicate that phonotactic knowledge exerts an extremely powerful force over speech perception. Not only do phonotactics influence classification of individual phonemes, the perception of illusory phonemes with no acoustic correlates can be induced. And it does it in non-degraded stimuli

Findings cont… Basically, people will not only assimilate nonnative sounds into native categories; people will invent or distort segments to make nonnative sounds fit the phonotactics of their language.

What does this mean? isn’t universal It tells us that the way that the continuous speech stream is divided into discrete phonemes isn’t universal; it depends on what the pattern of alternations between consonants and vowels is in the language in question.

The End