Perception of English Word-final Stops in Clearly ArticulatedConnected Speech by Japanese L2 Learners of English*
Kikuyo Ito
National Institute of Technology, Kagawa College
ABSTRACT. This study investigated the perception of place-of-articulation contrasts of English word-final
stops /p-t-k/, /b-d-g/, and /m-n-ŋ/ in running speech by adult Japanese second language (L2) learners of English,
using real words. Minimal triplets differing in place of articulation of the word-final stop (e.g., sip, sit, and sick),followed by adverbs starting with /p/, /t/, or /k/ in sentences were presented in clearly articulated speech.
Participants chose one of three written options of the target words after listening to a sentence, such as He said
the word sit positively (or tauntingly or cautiously).
Results showed that Japanese listeners had difficulty identifying word-final unreleased oral stops, indicating
their heavy reliance on the release. Japanese listeners also showed marked difficulty in correctly perceiving
word-final nasal stops, in contrast to American listeners' ceiling-level performance.
Keywords: L2 phonetic perception, word-final consonants, connected speech

1. Introduction
English word-final consonants are realized differently in connected speech from the sameword-final consonants produced in isolation because of coarticulation with the following
segment. Their realization also varies with speaking rate and style (e.g., Gay 1981; Manuel etal. 1992). Although some variations are reported to be less intelligible than their base forms(e.g., Householder 1956; Nolan 1992; Gaskell and Marslen-Wilson 2001), first language (L1)listeners generally seem to be capable of recovering the underlying forms of phonetic
segments from coarticulated speech when they are presented in context (e.g., Sumner andSamuel 2005; Gow 2002, 2003; Manuel 1995). In the case of non-native perception, however,
how well second language (L2) listeners can perceive the underlying representations ofphonetic segments in connected speech has not been well explored yet. The goal of thepresent study was to investigate L1 and L2 perception of English word-final oral and nasal
stops with different places of articulation in connected speech.
The study examined the identification of English words ending with an oral or nasal stop
followed by a word beginning with an oral stop /p/, /t/, or /k/ in clearly articulated connectedspeech. Native speakers of Japanese (JP) and American English (AE) participated in theexperiment.
Since the present study adopted real words for the target stimuli, the lexical influence onword identification was analyzed by examining the correlation of percent accuracy of theexperiment with word familiarity and with word frequency of the target words. The
correlations between perceptual performance of JP listeners and their length of residence(LOR) and age of arrival (AOA) in English-speaking countries, and their English proficiency
were also examined.
2. Methods
2.1. Participants
Twenty-four adult native speakers of JP living in the U.S. and a control group of
twelve adult native speakers of AE participated in the experiment. The information of JP and
AE participants is presented in Table 1.

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LanguageGroup
JP(N = 24)
AE(N = 12)

GenderDistribution
3 males
21 females
4 males
8 females

Mean Age(Range)32.3(22 – 44)30
(23 – 44)

Mean LOR(Range)5y 8m(1m – 17y 8m)

Mean AOA(Range)25.5(17 – 34)

Table 1 Biographical information on Japanese and AE participants
2.2. Stimulus Materials
A total of 54 target words, constituting 18 monosyllabic CVC minimal triplets, each ofwhich differed in only the place of articulation of the word-final stops, such as sip-sit-sick,lab-lad-lag, and sum-sun-sung, were constructed. (The places of articulation of the targetwords, Labial, Alveolar, and Velar, are called target place, hereafter.) These triplets were
subdivided into three groups, according to the types of contrast of the final stops (contrast
type, hereafter): Voiceless contrasts (/p/-/t/-/k/), Voiced contrasts (/b/-/d/-/g/), and Nasal
contrasts (/m/-/n/-/ŋ/).
The target words were followed by one of the following three adverbs: positively,tauntingly, or cautiously, creating a total of 162 two-word sequences. The two-wordsequences, therefore, contained 27 types of consonantal sequences at the word boundary: 9
final stops of the target words (/p/, /t/, /k/, /b/, /d/, /g/, /m/, /n/, and /ŋ/) × 3 initial stops of thefollowing adverbs (/p/, /t/, and /k/). In addition, a total of 72 filler sequences using
word-initial minimal triplets, such as pick-tick-kick were included. All two-word
combinations including the fillers are presented in the appendix.
All two-word sequences were preceded by “He said the word …” in the recording, suchas, “He said the word sit cautiously,” making syntactically and semantically viable English
sentences. The stimulus sentences were produced by a 29-year-old phonetically trained malenative speaker of AE from the New York area. The speaker was instructed to read thesentences “as if speaking to a non-native English listener or speaking in a noisy environment.”
All sentences were digitally recorded using a microphone (SHURE SM 48) in asound-attenuated room at a sampling rate of 22,050 Hz, monaural, with 16-bit resolution,
supported by SOUND FORGE 4.5 software.
A total of 468 stimulus sentences, which included two physically different tokens of 162
target and 72 filler sentences, were presented in the experiment.
The presence or absence of the oral stop release and the magnitude of the release,measured by multiplying the amplitude of each release by its duration, were examined andsummarized in Figure 1. The following context (following place, hereafter) was categorized
into Different or Same context for each contrast type, depending on whether the following
place coincides with the target place.
A clear pattern seen in the data is that the word-final stops of the target words (target
stops, hereafter) were not released in most cases in Same contexts whereas they were almost
always released in Different contexts. This pattern was seen in both Voiceless and Voiced
contrasts, and was most clearly seen in Labial in which the stops were never released in Same
contexts and were always released in Different contexts.

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Figure 1 Magnitude of Oral Stop Release Compared by Following Context
2.3. Procedures
Participants were tested individually in a sound-attenuated room in the
Speech-Language-Hearing Sciences department at the Graduate Center of the City Universityof New York, using the computer software, Paradigm. The experiment consisted of the main
experiment and a word familiarity rating task, both of which were self-paced, followed by astandardized English proficiency test called the VersantTM English Test (for JP participants
only). The entire session was completed within two hours for JP participants and within one
and a half hours for AE participants.
2.3.1. Main experiment
The stimuli were presented binaurally through headphones (Telephonics TDH 39) inrandom order. For each trial, a stimulus sentence with one member of a triplet as the target
word (e.g., “He said the word sit positively”) was presented, and participants were asked to
identify the target word by clicking on one of the three written alternatives appearing on thecomputer screen (e.g., sip, sit and sick).
The experiment consisted of 12 blocks, each of which contained 39 trials. One repetitionof each sentence was presented in the first 6 blocks and the other repetition in the remaining 6
blocks. In order to avoid fatigue effects, 5-minute breaks were inserted after the third, thesixth, and ninth blocks.
2.3.2. Word familiarity rating task
The main experiment was followed by a word familiarity rating task that asked
participants to rate their familiarity with the written target words by clicking on one of sevenboxes corresponding to the seven levels of familiarity (1 = I don't know the word at all, 7 = I
know the word very well).
2.3.3. Versant English test
The VersantTM English Test, a 20-minute computerized telephone test, was administeredonly to JP participants. It assesses English spoken language skills of non-native speakers by
the overall score with four diagnostic subscores (Pronunciation, Fluency, Sentence Mastery,and Vocabulary). It has been reported that extended one-on-one interviews by two experts
correlate scores greater than 90% (Bernstein 2009).

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3. Results
3.1. Language effect (AE vs. JP)

0

Target Stimuli

Fillers

Voiceless Voiced

Nasal

Contrast Type

Figure 2 Percent Correct Accuracy by JP and AE Listeners
The left panel in Figure 2 illustrates the overall response accuracy by AE and JP listeners.
The performance on the filler items by both JP and AE listeners was at ceiling level whereas
their performance on the target stimuli exhibited the language effect showing better
performance by AE listeners than JP listeners (median response accuracy 88.9% by JP vs.
98.5 % by AE). The overall response accuracy by AE listeners was significantly higher thanthat of JP listeners [Mann Whitney U, U = 3, z = -4.74, p < 0.001], with a very large effectsize [r = 0.79].
The JP and AE performance on each contrast type (Voiceless, Voiced, Nasal) is presented
in the right panel of Figure 2. The JP performance was significantly lower than the AE
performance on all contrast types [Mann Whitney U with Bonferroni adjustments, U = 63, z =-2.74, p < 0.01 for Voiceless, U = 48, z = -3.25, p < 0.001 for Voiced, U = 0, z = -4.84, p <0.001 for Nasal]. The language effect was larger for Nasal [r = 0.81] than for Voiceless [r =0.45] and Voiced [r = 0.53] contrasts.
Figure 3 shows the performance on each target place (Labial, Alveolar, Velar) of eachcontrast type. While the JP performance on Voiceless Alveolar /t/ and Voiced Alveolar /d/was significantly poorer than the AE performance [Mann Whitney U with Bonferroni
adjustments, p < 0.001 for /t/, p < 0.0056 for /d/] with large effect sizes [r = 0.53 for /t/, r =0.77 for /d/], their performance on Labial /p/, /b/ and Velar /k/, /g/ did not differ significantly
from that of AE listeners. The results indicate that the language effects observed for
Voiceless and Voiced contrasts are attributable to the JP group’s significantly worse
performance only on Alveolar stops. On the other hand, the JP performance on Nasal
contrasts of all target places were significantly worse than the corresponding AE performance,with very large to medium effects [r = 0.77 for /n/, r = 0.81 for /ŋ/, r = 0.49 for /m/].

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0LabialAlveolar

Velar

LabialAlveolar

Velar Labial

Alveolar

Velar

Target Place

Figure 3 Percent Correct Accuracy on Target Place by AE and JP Listeners
3.2. Contrast type comparisons (Voiceless vs. Voiced vs. Nasal)
The performance differences between contrast types and those between target places
within each contrast type were examined within each language group and are briefly
summarized below. For the AE group, a non-parametric Friedman's test and three separate
Wilcoxon Signed-Rank tests with Bonferroni adjustments were carried out because of theheterogeneity of variance and ceiling effects. A one-way repeated measures ANOVA andthree separate repeated measures ANOVAs with Bonferroni adjustments were adopted for the
JP group.
The AE performance on Voiceless contrasts was significantly worse than that on Voiced
contrasts and Nasal contrasts. The difference in performance between Voiced and Nasal
contrasts was not significant, showing the following relationship in terms of the goodness ofthe performance: Voiceless < Voiced ≈ Nasal. The results indicate that word-final voicelessstops are relatively harder to perceive than voiced and nasal counterparts even for native
listeners.
The JP performance on Nasal contrasts was significantly poorer than that on both Voiced
and Voiceless contrasts with very large effect sizes (ηp2 > 0.8 for both contrasts). The
difference in their performance between Voiced contrasts and Voiceless contrasts did not
differ significantly, showing the following relationship regarding the goodness of theperformance: Nasal < Voiceless ≈ Voiced. The results indicate marked difficulty in correctly
perceiving the place of articulation of word-final nasal stops in a sentence, showing a very
different perceptual pattern from that seen in the AE results.
3.3. Following place comparisons (Different vs. Same)
Wilcoxon Signed Rank Tests with Bonferroni adjustments revealed no significant
difference between Different and Same contexts in the AE performance except for VoicelessVelar /k/ that showed better performance on Different than on Same context.
The JP performance seemed to be more affected by following place. JP listeners' mean
response accuracies on Same and Different contexts with standard errors are presented in
Figure 4.

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**

**

**

**

Figure 4 Mean Percent Correct Accuracy by JP on Following Place
Repeated measures ANOVAs revealed that four out of nine target stimulus types showed
better performance on Different than on Same context and that Same context was neverperceived better than Different context in any of the contrast types in the JP performance.
Since the release of a word-final oral stop in Same context was either deleted or criticallyreduced, the JP listeners’ pattern showing better performance on Different context than on
Same context for oral stops suggests that JP listeners were utilizing stop release cues forplace identification of word-final oral stops. The next part examines the listeners’ reliance on
the release cues for the perception of word-final oral stops more directly by examining thecorrelations between the magnitude of the stop releases and the corresponding performance.
3.4. Correlations between magnitude of stop release and performance
The correlations between the magnitude of the oral stop releases of the target words withthe corresponding performance by JP and AE listeners were examined, by multiplying the
RMS amplitude of the release by duration as the indicator of the magnitude of the release.
Spearman rank order correlations revealed positive correlations of the JP performance on
both Voiceless [rho=0.55, p < 0.01] and Voiced [rho=0.34, p < 0.01] tokens, indicating JP
listeners’ heavy reliance, especially for Voiceless stops, on the place information in the stop
release. As for AE listeners, significant correlations were seen in performance on Voicelesstokens only [rho=0.300, p < 0.01], showing similar but much weaker patterns of correlations
than those of the JP performance.
3.5. Lexical effects on performance: word frequency and word familiarity
The lexical effects were analyzed by examining the correlation of performance on themain experiment with scores on the word familiarity task and with word frequency of thetarget words based on the SUBTLEXUS corpus. The SUBTLEXUS norms are reported to
predict lexical decision times quite consistently (Brysbaert and New 2009). Spearman
rank-order correlations showed no correlations between the percent correct accuracy on targetwords and the corresponding word familiarity scores by either of the language groups. Noneof the correlations between the response accuracy and word frequency scores were significant
either, indicating that there were no lexical effects on the performance.
3.6. Correlations with LOR, AOA, and language proficiency.
The correlations of the JP listeners’ performance with their LOR, AOA, and English
proficiency measured by the VersantTM English Test (Versant Test, hereafter) were examinedby adopting Spearman rank order correlations. The scatter plots showing the correlations of― 114 ―

Overall % correct

the overall accuracy of JP listeners with their LOR, AOA, and Versant Test scores arepresented in Figure 5. Strong positive correlations of LOR were seen not only with theoverall performance but also with the performance on all three contrast groups.
The correlations of the JP listeners’ performance with their AOA were much weaker
than those with LOR. A significant negative correlation was only seen with the performanceon Voiceless contrasts.
The correlations of the JP performance with the overall scores of the Versant Test were
almost as strong as those of LOR. Among the subscores of the Versant Test, Pronunciation
and Fluency scores showed higher correlations with performance than the other subscores.

rho = .729**
LOR (months)

rho = -.253
AOA (age)rho = .658**
Overall Versant Score (20-80)

Figure 5 Correlations of JP Performance with LOR, AOA, and Language Proficiency
4. Discussion
Results of the present study indicated that the language effect predicting less accurate
perception by JP than AE listeners was evident in the performance of the main experiment on
all contrast types. No correlations between performance and word familiarity or word
frequency were found in either of the language groups, indicating no lexical effects on theirplace perception of word-final stops in connected speech. Perceptual patterns by JP and AE
listeners observed in this study are discussed below.
4.1. JP listeners’ perceptual difficulty in identifying word-final nasal stop
The JP listeners’ difficulty in identifying word-final nasal stops was clearly indicated in
the result showing the JP group's much lower performance on Nasal contrasts than thecorresponding AE performance, as well as in the result showing the JP group’s much poorer
performance on Nasal contrasts than their performance on Voiceless and on Voiced contrasts.
The observed difficulty by JP listeners is explicable by attributing it to the negative L1
influence caused by the place assimilatory nature of the Japanese moraic nasal. The place ofarticulation of the moraic nasal /N/ is underspecified because of its obligatory placeassimilation to the following segment, resulting in several allophonic variations including [m],[n] and [ŋ] (Amanuma et al. 1983; Vance 1987; Nakajo 1990). This archiphonemic nature ofJapanese moraic /N/ create L1-based perceptual patterns of syllable-final nasals by JPlisteners (e.g., Otake et al. 1993, 1996), which are likely to be applied to non-native inputs(e.g., Cutler and Otake 1994, 1998). Aoyama (2003) reported that these L1-based perceptual
patterns cause confusion in identifying the place of articulation of English word-final nasals
produced in isolation. The results of the present study support the Aoyama study, extending
the argument to the perception of English word-final nasals followed by other consonants inconnected speech.

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4.2. Influence of oral stop releases on performance
Results comparing the performance on Same and Different contexts of Voiceless andVoiced contrasts revealed that the JP performance in Same contexts was less accurate thanthat in Different contexts for the target places /p/, /k/, and /b/. No significant trend in the
opposite direction was found. The AE performance showed no difference between Different
and Same contexts except for /k/, which showed better performance on Different than on
Same context.
The JP listeners’ less accurate perception of oral stop contrasts in Same context than in
Different context suggests their heavy reliance on acoustic information in stop releases
because the release of a word-final oral stop in Same context was either deleted or criticallyreduced. The positive correlations between the magnitudes of the oral stop releases and the JP
performance on the corresponding tokens strongly supported this assumption. The AE
performance on Voiceless contrasts showed a weaker positive correlation, but theirperformance on Voiced contrasts did not show a correlation, indicating that AE listeners weremuch less dependent on the acoustic cues in stop releases. The results are consistent with pastfindings that listeners whose L1 has no or limited word-final stops rely on L2 stop releases(e.g., Flege 1989; Flege and Wang 1989) and that AE listeners are able to tap into
anticipatory acoustic information available in the preceding vowel and transitional segmentsof English word-final stops (Warren and Marslen-Wilson 1987, 1988).
4.3. Correlations of JP Performance with language experience and proficiency
The JP listeners’ overall performance as well as their performance on all contrast types
was more strongly correlated with their LOR than AOA, indicating that LOR is a better
predictor of performance. In the scatter plots, however, the improvement of the performance
as a function of LOR is not clearly seen after four to five years of LOR, which may indicate apossible cut-off point of the effects of L2 immersion on perceptual accuracy. Thisobservation is in line with the notion that a long LOR alone may not guarantee the acquisitionof difficult L2 contrasts, as has often been pointed out by Flege and colleagues (e.g. Flegeand Liu 2001).
The JP performance on all contrast types was also positively correlated with theirlanguage proficiency as measured by the Versant Test. Among the subscores, thepronunciation score and fluency score were better correlated with the performance than thesentence mastery score and the vocabulary score, suggesting a close relationship between L2phonetic perception in connected speech and L2 production skills.
4.4. Future direction
The present study is based on the author's dissertation study, which investigated the JP
listeners' place perception of English word-final stops followed by word-initial stops inclearly articulated speech (clear speech, hereafter), as well as in casually produced fastspeech (fast speech, hereafter). The current study only reported the results from clear speech,
setting a starting point for the entire dissertation study and the following extension studies.
The next paper will report findings from comparisons of the data for clear speech withanother set of data for fast speech. In addition, the same experiment using the fast speechstimuli were administered to the same number of Korean listeners to confirm the notion thatJP listeners’ difficulty in identifying word-final nasals is due to the negative influence of L1
phonology. The report of the Korean study will follow the dissertation study. Furthermore,
supported by a Grant-in-Aid for Scientific Research, or KAKENHI, a new set of follow-up― 116 ―

studies using the same experimental paradigm with the stimulus materials from newrecordings by multiple speakers of AE are in preparation to establish a series of studies, theaccumulated findings of which would make a contribution to the area of cross-language
speech perception.
Note*The present study is written based on my dissertation study submitted to the Ph.D. program in
Speech-Language-Hearing Sciences at the Graduate Center of the City University of New York. I would like tothank the members of the supervisory committee of the dissertation, Dr. Winifred Strange, Dr. Klara Marton, Dr.
Valerie Shafer, Dr. Lisa Davidson, and Dr. Douglas Whalen. This material is based upon work supported by the
National Science Foundation under Grant No. BCS-1023192.

Appendix
Stimulus Sentence List
Target Words (word-final minimal triplets: 54 words)
contrast typevowel
minimal triplet stimuli
sip-sit-sick/ɪ/
lip-lit-lick/p/-/t/-/k/
sap-sat-sack/æ/
rap-rat-rackshop-shot-shock/ɑ/ or /ʌ/hop-hot-hock
rib-rid-rig/ɪ/bib-bid-big/b/-/d/-/g/
tab-tad-tag/æ/lab-lad-lag
cob-cod-cog/ɑ/ or /ʌ/dub-dud-dug
dim-din-ding/ɪ/
Kim-kin-king/m/-/n/-/ŋ/
ram-ran-rang/æ/bam-ban-bang
sum-sun-sung/ɑ/ or /ʌ/
rum-run-rungFillers (word-initial minimal triplets: 24 words)
contrast typeminimal triplet stimuli
pick-tick-kick/p/-/t/-/k/
puff-tough-cuff
pan-tan-can
bet-debt-get/b/-/d/-/g/bun-done-gun
bait-date-gate
mock-knock-(dock)/m/-/n/mitt-knit-(bit)map-nap-(gap)

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Adverbpositively

tauntingly

cautiously

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