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and Speech
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Tone Perception Ability of Cantonese-Speaking Children
Kathy Yuet Sheung Lee, Sung Nok Chiu and Charles Andrew van Hasselt
Language and Speech 2002 45: 387
DOI: 10.1177/00238309020450040401
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LAN GUAGE AND SPEECH, 2002, 45 (4), 387 – 406
387
Tone Perception A bility
of Cantonese-Speaking Children*
Kathy Yuet Sheung Lee1
Sung Nok Chiu2
Charles Andrew van Hasselt1
1 The
Chinese University of Hong Kong, Hong Kong
Kong Baptist University, Hong Kong
2 Hong
Key words
Cantonese
F0 onset and
offset
lexical knowledge
tone perception
Abstract
Studies have shown that while children acquire all Cantonese tones by age
two, they are not able to label them reliably until approximately age 10. One
possible explanation for the large age discrepancy may be t he different
methodologies used. This study aimed to (1) investigate a new research design
for the collection of reliable tone perception data from young children; (2)
compare lexical and nonlexical items for testing tone perception ability; and
(3) identify the relative ease of perceiving the three basic tone contrasts in
Cantonese, that is, high level/ high rising (T1 / T2), high level/ low falling
(T1/ T4), and, high rising / low falling tones (T2 / T4).
The three tone pairs were presented to 31 children in the form of word and
nonword stimuli. It was found that the research design could be used to assess the tone perception
knowledge of children as young as 2;09. Significant differences were found between word and nonword
stimuli and also in the identification of the T2 / T4 contrast in comparison with the other two pairs.
Children’s overall tone perception abilities are discussed in detail with reference to the role of
lexical knowledge and the potential for tone perception confusions arising from differences in
fundamental frequencies for tone onset and offset.
1 Introduction
Cantonese, a dialect spoken in H ong Kong, M acau and the province of G uangdong in
China, is one of the world’s many tone languages, which use differences in the pitch of
the speaker’s voice to distinguish one word from another (Bauer & Benedict, 1997).
* Acknowledgments: The research was supported by a grant from the Health Services Research
Committee (G rant N umb er 831019). We thank D r. G odfrey H arrison for his helpful
comments on an earlier draft of this paper, the two referees and D r. M arilyn Vihman for
their detailed and thorough review which improved the paper substantially, M s. Pheobe Lo
for recruiting subjects, M s. Livia Wong for data collection, M s. Pamela Cheung for drawing
pictures and M s. Johanna Barry for the final editing work. We are also grateful to all the
parents and children who took part in the study.
Address for correspondence: Prof. C. A. van H asselt / Kathy Y. S. Lee, D ept. of Surgery,
The Chinese U niversity of H ong Kong, Prince of Wales H ospital, Shatin, H ong Kong;
e-mail: < [email protected]> / < [email protected]> .
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Tone perception ability of Cantonese-speaking children
There are six contrastive tones in Cantonese (M atthews & Yip, 1994); they are distinguished by fundamental frequency (F 0) in terms of height, contour and direction
(G andour, 1981). U sing the computer software D r. Speech (D r. Speech — software
group, Tiger D R S, 1998), F igure 1 was constructed to illustrate the different fundamental frequency patterns of the six tones spoken by a female experimenter in this
study.
Figure 1
The different fundamental frequency patterns of the six Cantonese tones on the vowel /a/
As shown in F igure 1, Tone 1 is high level. H owever, it can also take the form of
a high falling contour. According to Chao’s interpretation (1947), the high level and high
falling fundamental frequency patterns of Tone 1 are allophones of the high level tone.
Tone 2 is high rising while Tone 5 is low rising. Tones 3 and 6 are mid and low level tones,
respectively. Tone 4 is low falling.
Previous studies of Cantonese tones in children have mainly focused on acquisition and perception. Based on the principle that comprehension precedes production
in child language development, a child who produces tones correctly should also be
able to perceive them correctly. However, a comparison of research data from the perception and production studies reveals a marked discrepancy in observations. Several
studies have demonstrated that children can produce all six tones in Cantonese by age
two (D odd & So, 1994; Tang & M aidment, 1996; Tse, 1978), but they have been found
to be unable to identify them all correctly before the age of 10 (Ching, 1984; Ching, 1990;
Lui, 2000).
One possible explanation for the discrepancies between the two study types may
be different data collection methods. Speech acquisition studies generally involve the
collection of spontaneous speech samples; hence they do not require children to follow
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K. Y. S. Lee, S. N. Chiu, and C. A. van Hasselt
389
difficult test instructions. Tones produced in speech samples may be vocalizations that
do not form meaningful words. In perception studies, on the other hand, participants
have to follow specific test instructions. The testing requires the child to overcome
stranger anxiety, to be compliant to testing instructions, to be cooperative and to have
a good attention span. A stimulus-response test paradigm which requires the child to
point to a picture / word card after the presentation of the stimulus has the significant
limitation that a reliable response pattern can only be consistently established for child ren aged fro m 30 – 35 m ont hs and older (H o dgson , 1994; M cCor m ick, 1992).
F urthermore, such a task is linguistically demanding and is only appropriate for use with
participants who are already familiar with the words in the task. There is thus a significant limitation on the age and type of child who can be recruited to participate in such
perception studies. Four-year-old children have so far been the youngest age group to
have participated in tone perception studies with Cantonese (Aisha, 2000; Ching, 1984;
Ching, 1990; Lui, 2000).
The present study aimed at investigating the tone perception abilities of threeyear-olds and further aimed to expand current understanding of children’s tone perception
abilities. This age range was considered suitable for such testing since M cCormick (1992)
and H odgson (1994) have found that this age group can perform reliably on the stimulus-response task.
Inclusion of all six tones was considered too difficult for children in this age range.
Thus fewer tones were used to ensure successful test completion and reliable response
rates. A number of studies have revealed that three tones are produced earlier and are
easier to identify (Cheung, 1995; Ching, 1988; Ching, 1990; Fok, 1984; Lee, Cheung, Chan,
& van H asselt, 1997; Tse, 1978; Varley & So, 1995). They are high level (T1), high rising
(T2) and low falling (T4) tones. The relative ease of identification reflects the fact that
they have higher frequencies of occurrence, have relatively higher intensity levels and
are perceptually more salient in terms of their marked differences in the contour and
pitch heights (Ching, 1984; Fok, 1974). We will refer to the three tones as basic.
The three tone contrasts— T1/ T2, T1/ T4 and T2/ T4 —were formed by combining
the three basic tones. We were interested in determining their relative ease of identification. U sing the two dimensions of pitch height and contour identified by G andour
(1981, 1983), tone identification difficulty has been addressed in a number of investigations. In studies with hearing-impaired children Fok (1984) adopted a high falling
contour as her T1 stimulus to contrast with T2 (different contour) and T4 (different height).
Children found it easier to identify pitch height (T1 / T4) than contour movements
(T1/ T2). Ching (1988), also working with impaired hearing participants, applied ’sequential information analysis’ and reported that pitch height accounted for most of the
information transmitted. Thus both Fok (1984) and Ching (1988) concluded that pitch
height was perceptually more salient than pitch contour for listeners with impaired
hearing. U sing the same sequential information analysis on alaryngeal speech with
normal hearing adults as listeners, Ching, Williams, & van H asselt (1994) found that
pitch contour was the more salient cue, however.
As for the studies with normal hearing participants, Ching (1984) did not analyze
the two dimensions in detail but pointed out that children confused tones 3 and 6 due
to the similarity of pitch height, while the difficulty with tones 5 and 6 stemmed from
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Tone perception ability of Cantonese-speaking children
a confusion of pitch contour. Based on Ching’s (1984) study, the data of Lui (2000) showed
that while some tone pairs involving differences in pitch height had higher scores (T1/ T6,
T1 / T3), others (T 3 / T6, T2 / T5) had lower scores when compared with tone pairs
differing in contour (T1 / T2, T5 / T6, T4 / T5, T4 / T6). For adults, Varley and So (1995)
found that tone pairs with similar onset pitch heights and / or pitch contour resulted in
comparable error rates. They concluded that both dimensions were equally important
for tone perception.
In this study, T1 / T2 share the same pitch height but different pitch contour (level
vs. rising) while T1 / T4 and T2 / T4 differ in both height and contour. We expected that
tone identification on T1 / T2 would be more difficult than the latter two contrasts as
T1 / T2 differ in one dimension only.
When testing young children the linguistic factor tends to confound results (Tyler,
1993). In picture identification tasks children need to be able to relate each word to the
appropriate picture (Barton, 1980). The syllable /ji/ occurs with all six tones in Cantonese
and is commonly used for tone identification studies (Aisha, 2000; Ching, 1984; Ching,
1988; Ching, 1990; Fok, 1984; Lui, 2000). H owever, the validity of its use when testing
young children is questionable since not all children are equally familiar with all six words,
for example, /ji 1 / ‘clothes’, /ji 2 / ‘chair’ and /ji 4 / ‘son’ are used in written Chinese but
are not colloquial Cantonese terms and could be foreign to young children. Others,
like /ji 3/, are only meaningful when combined with other syllables to form multisyllabic
words such as / ji3 tai6 lei6 fán2 / ‘spaghetti’. The database compiled by F letcher, Stokes,
Leung, & Weizman (2000) included 332 different word tokens produced by five two-yearolds and 594 from 10 three-year-olds. The word /ji/ occurred on the list only with T6
(meaning ‘two’), suggesting that the /ji/ stimuli were outside children’s common experience. Even if children undergo a training session to learn all the words before the test
commences, the distortion due to differences in linguistic familiarity will remain. Such
effects have been found to be closely related to the number of errors made in perception tasks (Barton, 1980). One way to minimize the effect is to use stimuli that stay
within the participants’ receptive lexical inventory. The lexical advantage for linguistically more precocious children will thus be minimized. Another way to control differences
in word familiarity among test participants is to use nonwords as stimuli. When presenting
the test stimuli, children are forced to respond using perceptual ability alone.
Words and nonwords have been widely used in the literature to examine phonological processing, lexical representation and memory (Bowey, 1997; G athercole &
Baddeley, 1997; G erken, M urphy, & Aslin, 1995; M cKone, 1995; Pitt, 1995). Similar
studies on tone perception are rare, however. One such study was by Cutler and Chen
(1997), who compared the performance of D utch and Cantonese listeners making samedifferent judgments on Cantonese words and nonwords. The assumption was that
linguistic knowledge would facilitate tone processing, and native speakers of Cantonese
would perform significantly better than non-native speakers on the task. The hypothesis was not supported, however, as the two groups performed similarly. By contrast,
Lee, Vakoch, and Wurm (1996) did find a positive effect for linguistic experience on
tone processing. U sing Cantonese, M andarin and English speaking adults as respondents, they found that native speakers were more successful at discriminating tones
from their own languages for both words and nonwords.
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K. Y. S. Lee, S. N. Chiu, and C. A. van Hasselt
391
The different conclusions arrived at the two studies may be related to the time
factor. The procedure used by Cutler and Chen (1997) was a speeded-response task
where only two seconds were allowed for participants to make responses. The interval
between presenting the two stimuli and making a same-different judgment was 400 ms.
In Lee, Vakoch, and Wurm’s study (1996), no time limit was imposed on participants
for making a response though they were asked to respond as accurately and quickly as
possible. The interstimulus interval was either five seconds or immediate presentation.
Lee, Vakoch, and Wurm (1996) reported significantly higher error rates with shorter interstimulus interval. The 400 ms interstimulus interval used by Cutler and Chen (1997)
was even shorter than five seconds used by Lee, Vakoch, and Wurm (1996). Test participants thus had less time for storing the first stimulus for later comparison. The imposition
of the two second rule for making a response may also have effectively inhibited participants’ access to linguistic representations, hence masking any positive effects due to
lexical knowledge.
There have been no studies using both words and nonwords to examine the role
of linguistic knowledge in Cantonese tone perception for children. Clumeck (1980)
investigated tone recognition abilities and attempted to find minimal pairs of real words
that were familiar to the children learning Mandarin. However, he failed to find one with
the rising tone to contrast with the low-dipping tone. As a result, he used a nonword
instead. H is two participants were unable to distinguish the tone pair. On being tested
for other tone contrasts where words were used, correct identification was consistently
exhibited. It was unclear what effect the use of a nonword had in contributing to the
observation that the rising and low-dipping tone distinction was difficult to perceive.
As far as the authors are aware, no further studies using words and nonwords for testing
tone perception in M andarin have been published. The effect of linguistic knowledge
on tone processing remains unclear for Cantonese-speaking children as well.
Based on the fact that children master tone production by the age of two, we
believe children should be able to reliably identify all tones in Cantonese at less than
four years of age, and that it is due to a limitation in research methodology that young
children’s tone perception ability has previously been underestimated. In this study we
aimed to test the tone perception abilities of children as young as three by limiting the
number of tones from six to three and by controlling for the confounding variable of
linguistic knowledge. The latter was achieved by using words within the child’s vocabulary and by including a series of nonwords as test stimuli. The use of word and nonword
stimuli was also important for determining the effect of linguistic knowledge on tone
processing.
Three main goals motivated this research: (1) to determine if the research design
was suitable for assessing the tone perception ability of children younger than four
years of age; (2) to determine if lexical or nonlexical items are better for assessing tone
perception, and (3) to determine the relative ease of identifying the three basic tone
contrasts of T1 / T2, T1 / T4, and T2 / T4.
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Tone perception ability of Cantonese-speaking children
2 Method
2.1
Subjects
Participants were recruited on a voluntary basis from preschool centers and from among
children who had previously been involved in a screening program for otitis media with
effusion (Tong, Yue, Ku, Lo, & van H asselt, 2000). The selection criteria were: (1) age
range from 2;09 to 3;03; (2) Cantonese as first language; (3) no abnormalities in overall
cognitive development reported by teachers or parents; and, (4) normal hearing and
language development as assessed during hearing and language screenings conducted
by qualified audiologists and speech therapists. For hearing screening, children were
tested with tone frequencies at 500, 1000, 2000, and 4000H z at 20dB H L (A scale). For
language screening, the Cantonese Receptive Vocabulary Test (Lee, Lee, & Cheung,
1996), a test standardized on 609 Cantonese-speaking children, was used. The passing
criterion was that the receptive vocabulary age equivalent score was greater than or
equal to the child’s chronological age. Among the recruited participants (n = 71), 32
(45%) fulfilled the criteria. Of these, one child did not complete testing, leaving a total
of 16 girls and 15 boys in the participant pool.
2.2
Test stimuli
Tone pairs. Three tone pairs were selected. These were T1 / T2, T1 / T4, and T2 / T4.
Tone 1 wa s presented as a high level tone throughout the test. Each tone pair was
presented using both word and nonword stimuli.
Word stimuli. A list of tone pairs was developed to meet three criteria: (1) minimal
pairs contrasting in tone only, (2) familiarity to three-year-old children, and (3) readiness for representation in picture format. A total of 32 pairs involving 49 words were
suggested (fifteen T1 vs. T2, nine T1 vs. T4, and eight T2 vs. T4). Out of the 32 pairs,
15 pairs were made into five trios using 15 words. The remaining 17 pairs involved 34
words. The words were reviewed by two speech therapists with six or more years of
experience in managing pediatric speech and language cases who agreed that the pool
could be regarded as an exhaustive list and no more pairs could be added. The minimal
pairs of words were then represented in line drawings m easuring 15 cm ´ 12 cm.
Appendix 1 displays the list of test items.
Nonword stimuli. The same vowel /a/ in the three basic tones were used in the nonword
stimuli. The syllable structure of a vowel alone, instead of (consonant) - vowel- (consonant), was selected so as to avoid coarticulation variations that might arise from different
consonant contexts.
Mode of presentation. Since test participants were three-year-olds with relatively limited
language ability and attention span, we chose live voice presentation to maximize
response success rate. Children have been shown to perform significantly better with live
voice presentation than with recorded speech (K irk & Lento, 2000). Varley and So
(1995) also commented that participants with a range of cognitive factors such as difficulties with attention control respond better to live than to recorded presentations.
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The use of live voice mode made it possible to present the stimuli in isolation. Tone
represents relative pitch information and listeners need to access the speaker’s overall
fundamental frequency range before making a correct tone perception judgment. For this
reason, stimuli used in recorded mode need to be presented in framed sentences. The
necessity of using a sentence does not apply in the case of live voice presentation since
participants have had sufficient opportunity to interact with the speaker to accommodate to his/ her relative pitch range before having to make tone perception judgments. An
advantage of using stimuli in isolation is that pitch differences among tones are greater
in citation form. Fok (1974) found that tones spoken in isolation covered a wider frequency
range than those spoke within a sentence frame since speakers were more conscious of
the tonal opposition in the former case. The use of tone in isolation also overcomes the
confounding variable of intonation patterns such as the sentence-final tone lowering
effect (Vance, 1976) and increases in tone levels in emphatic speech (Fok, 1974). Citation
form tones would thus be predicted to be easier for young children to label correctly due
to their reduced pitch variability and greater between-tone pitch differences.
2.3
Test procedures
The test protocol involved three stages: (1) word comprehension check, (2) tone test
using words, and (3) tone test using nonwords.
2.3.1
Stage 1— Comprehension check
Any speech perception test involving the use of words has to ensure that a participant’s
failure to identify cannot be ascribed to his limited vocabulary (H nath-Chisolm, &
Boothroyd, 1998). There was no Cantonese database to indicate the extent of children’s
vocabulary in the age range of this study. The comprehension check was designed to
control for children’s vocabulary knowledge.
The 49 words to be used as stimuli were arranged into 13 test plates, each comprised
of four line drawings depicting the four words. Words in each test plate were arranged
so that they represented different tones and different phonemic segments. In the test children were asked to point to the named pictures. The results obtained in the comprehension
check formed the basis for selecting items for the second stage of the study. The item
list comprising the comprehension check is provided in Appendix 2.
2.3.2
Stage 2 —Tone test using words
At this stage, the “tone test form,” which consisted of 32 minimal pairs, was employed
in test administration. U sing the results from the preceding comprehension test, the
only items administered were those for which the child knew both words in the minimal
pair contrast. While each tone pair was randomly presented in five trials with the target
words, the actual number of total trials varied from child to child depending on the number
of available testable pairs. Table 1 (overleaf) summarizes the number of testable pairs
for each participant based on the comprehension check. For instance, one child could
be tested on seven test pairs for the T1 / T2 contra st; the total number of trials he
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Tone perception ability of Cantonese-speaking children
attempted for the T1 / T2 contrast was thus 35 (7 pairs ´ 5 trials each). Another child
could not be tested for any T1 / T4 or T2 / T4 contrast; this child was not tested on the
two contrast types. D uring the test, the experimenter read aloud selected tone pairs
from the tone test form. The participants pointed to the pictures that they believed
represented the words. For each tone pair, each child was scored based on the number
of correct responses out of the total number of trials presented.
TABLE 1
Number of testable pairs based on the comprehension check
Tone pairs
Number of testable pairs
H igh level versus high rising (T1 / T2)
3
4
5
6
7
Number of subjects
11
16
3
0
1
Total 31
H igh level versus low falling (T1/ T4)
0
3
4
5
1
13
15
2
Total 31
H igh rising versus low falling (T2 / T4)
0
1
2
3
4
5
1
6
2
10
11
1
Total 31
Stage 3 —Tone test using nonwords
As in the second stage, the three tone pair contrasts (T1 / T2, T1 / T4, and T2 / T4) were
used, but nonwords instead of words were used as test stimuli in this stage.
Each tone pair contrast (T1 / T2, T1 / T4, and T2 / T4), presented as a repeat of the
vowel /a/ , was randomly presented in five trials, leading to a total of 15 trials (3 tone
contrasts ´ 5 trials each).
Three dolls from the toy set “M r. Potato H eads” were used as test materials. The
dolls possessed distinctive facial expressions and costumes. Each doll was given a name
corresponding to a tone. M ore precisely, the names were / a a / in tone 1, 2 or 4. Before
the responses were scored, the names of the two dolls were each presented twice for the
participants to learn. The children indicated understanding by either pointing to the
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K. Y. S. Lee, S. N. Chiu, and C. A. van Hasselt
395
corresponding doll or by spontaneous imitation after the experimenter. After the practice trials, participants were asked to feed the named doll with a color marble. The order
of presentation for the target stimuli within each tone pair was randomized. For each
nonword tone pair, each child was scored based on the proportion of trials in which correct
responses were made.
2.4
Order of presentation
As children found the names of the dolls in the nonword condition highly confusing
when presented repeatedly, an alternating presentation of word and nonword stimuli
was used as follows:
word stimuli T1 / T2 ® nonword stimuli T1 / T2 ® word stimuli T1 / T4
stimuli T1 / T4 ® word stimuli T2 / T4 ® nonword stimuli T2 / T4.
®
nonword
2.5
Test environment
The testing procedure wa s conducted in a soundproof booth. The two testers were
qualified female speech therapists who had undergone a 30 mins training and practice
session in monitored live voice presentation. The practice aimed at achieving production of all stimuli, regardless of tone, at 65dB (A scale) ± 5dB levels. The training target
was achieved with the aid of a sound level meter (Bruel & K jaer 2238 M ediator integrating sound level meter — basic SLM software BZ 7126, Bruel, & K jaer Sound &
Vibration Measurement A / S, N oerum, Denmark, 1998), which was also used to monitor
voice intensity during testing sessions.
3 Results
A logistic regression (Agresti, 1990; F isher & van Belle, 1993; Rasch, 1960)
ln [pijk / (1 – pijk ) ] =
a
i
+ wj + Tk ,
was used to analyze the dichotomous data (success and failure) from all trials to examine
whether the scores observed depended on the participants’ tone perception ability, the
lexical status of the stimulus (i.e., word vs. nonword) or the tone contrast pair (T1 / T2,
T1/ T4, and T2/ T4). In the model, pijk is the probability that the i th participant correctly
identified the kth tone pair (k = 1, 2, and 3 for T1 / T2, T1 / T4, and T2 / T4 respectively)
of words if j = 0 or nonwords if j = 1, a i is the tone perception ability measure for the
ith participant and, wj and Tk are the difficulty measures of the j th lexical status and
the kth tone pair, respectively.
There were 31 participants and six types of questions (wo rd vs. nonword for
T1 / T2, T1 / T4, and T2 / T4). Appendix 3 summarizes the scores obtained for the study
sample (n = 31). U sing the G EN M OD procedure in SAS 8.0, a statistically significant
difference in the participants’ ability to make correct responses was found (p < .0001).
The probability pijk was influenced by the lexical status (p < .0001) as well as the combination of tone pairs (p = .0004). N o significant interaction was observed between the
lexical status and combination of tone pair (p = .2850).
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Tone perception ability of Cantonese-speaking children
Table 2 summarizes the descriptive statistics for the participants’responses which
were obtained from the logistic regression. We used the model’s predicted values because
they smoothed the data and provided improved estimates. The highest and lowest
possible scores for each participant were 1 and 0, respectively.
TABLE 2
Descriptive statistics for the model-based scores for the study sample (n = 31)
Tone Pairs
Word
Nonword
H igh Level (T1)
M ean
0.93
0.77
vs. H igh R ising (T2)
M in
0.76
0.42
M ax
1.00
1.00
Range
0.24
0.58
SD
0.06
0.15
95% CI
0.91– 0.95
0.72– 0.83
H igh Level (T1)
M ean
0.92
0.75
vs. Low Falling (T4)
M in
0.73
0.39
M ax
1.00
1.00
Range
0.27
0.61
SD
0.06
0.16
95% CI
0.90– 0.94
0.69– 0.80
H igh R ising (T2)
M ean
0.87
0.66
vs. Low Falling (T4)
M in
0.62
0.28
M ax
1.00
1.00
Range
0.38
0.72
SD
0.09
0.20
95% CI
0.84– 0.91
0.59– 0.73
SD = standard deviation; CI = confidence interval.
As shown in Table 2, the participants had a higher overall average probability of
making correct responses for words than for nonwords. The ranges and the standard
deviations for the scores indicated that intersubject variability was higher with nonwords
than that with words.
Likelihood ratio statistics were employed to examine intergroup differences between
the three tone pairs in the logistic regression model. The differences between identifying T2/ T4 with T1/ T2 and with T1/T4 were significant (p= .0002 and .0028 respectively).
The lowest mean score was obtained for the T2 / T4 tone contrast, indicating that this
was the most difficult contrast to label correctly. N o significant difference was found
when contrasting T1 / T2 and T1 / T4 identification (p = .4396).
M ore precise fundamental frequency measurements were obtained to further investigate the observed differences in the relative ease with which the contrasts were identified.
Table 3 summarizes the average F 0 values obtained for the onsets and offsets of the three
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K. Y. S. Lee, S. N. Chiu, and C. A. van Hasselt
397
tones based on measurements on the vowel /a / averaged over 10 productions for each
of the two female experimenters in this study. Values reported by Bauer and Benedict
(1997) on two female Cantonese speakers in H ong Kong are included for comparison.
TABLE 3
Average F 0 values at onset and offset for the three tones
T1 ( HL)
T2 ( HR)
T4 ( LF)
Average F0 at:
onset
offset
onset
offset
onset
offset
Speaker 1 in this study
245.4
236.6
169.2
253.4
173.1 131.9
Speaker 2 in this study
290.8
298.9
200.3
293.8
197.7 158.3
Speaker 1 in Bauer & Benedict (1997)
245.2
266.7
218.8
285.2
223.0 178.0
Speaker 2 in Bauer & Benedict (1997)
255.4
331.9
205.4
346.5
206.7 186.5
TABLE 4
D ifferences in F 0 values at onset and offset for the three tone contrasts
T1 / T4
T1 / T2
T2 / T4
Difference in F0 at:
onset
offset
onset
offset
onset
offset
Speaker 1 in this study
72.3
104.7
76.2
16.8
3.9
121.5
Speaker 2 in this study
93.1
140.6
90.5
5.1
2.6
135.5
Speaker 1 in Bauer & Benedict (1997)
22.2
88.7
26.4
18.5
4.2
107.2
Speaker 2 in Bauer & Benedict (1997)
48.7
145.4
50.0
14.6
1.3
160.0
Table 4 shows the differences in F 0 values at onset and offset for the three tone
contrasts. Substantial differences in F 0 values for both onset and offset were observed
for the T1/ T4 pair. The T1/ T2 differed significantly in onset F 0 value but much smaller
differences in F 0 offset values were measured. T2 / T4 has the reverse pattern, that is, a
small onset F 0 difference but a marked difference in F 0 offset value.
4 Discussion
4.1
Overall tone perception performance
This study has found an average probability of correct tone identification of 0.91, which
is substantially higher than the means of 0.32 and 0.66 given in Ching (1984) and Lui
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Tone perception ability of Cantonese-speaking children
(2000). An attempt was made to establish the reasons for these differences by comparing
the methodological approaches in the three studies (Table 5).
TABLE 5
Comparison of the three related studies investigating Cantonese tone perception in normal
hearing children
Present study
Ching, 1984
Lui, 2000
Age of subjects used
for comparison
2;09 – 3;03
4;00
4;00– 4;11
N umber of subjects
in the group
31
N ot specified
15
N umber of tones studied
3
6
6
In isolation
In isolation
Embedded in the
middle of a
carrier phrase
In the child’s
vocabulary inventory#
The six tone
contrasts on /ji/
The six tone
contrasts on /ji/
M ode of presentation
M onitored live
voice
Recorded
presentation
Recorded
presentation
M ode of response
required from subjects
Picture pointing#
Picture pointing
Picture pointing
N umber of choices given
in each test item
2
6
2
Overall tone identification
score on all six tones
No information
0.33
0.69
Overall tone identification
score on T1, T2 and T4
0.91#
0.32
Around 0.66*
Format of stimuli
presentation
Stimulus Words
*F igure obtained by estimation on graph, exact figure not available.
#
Refer to the experimantal condition of using word stimuli in the present study.
Lui (2000) based her study design on Ching (1984) and made two major modifications. F irstly, the number of choices given to the participants was reduced from six
to two. Secondly, she presented the target word in a carrier phrase instead of in isolation. The superior tone identification score in Lui’s study suggests that modifications
to the research design were well suited to the task abilities of four-year-olds. We believe
that the use of the two-choice format in testing young children is an appropriate design
since it greatly reduces the cognitive load required.
The effect of reduced response choice and of presenting the target word in a carrier
phrase can be explored by comparing the present study with Lui’s. Participants in this
study had a higher average score suggesting that there was no advantage in using medial
positioning for stimulus presentation as used by Lui (2000), that is, children seemed to
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K. Y. S. Lee, S. N. Chiu, and C. A. van Hasselt
399
have no problem in extracting speakers’ relative pitch level during monitored live voice
presentation even when the stimuli were presented in isolation. On the contrary, presenting
in isolation may focus children’s attention on the stimuli and thus yield more accurate
judgments.
U sing words that were in the child’s inventory as test stimuli also had an important effect. We believe that employing a comprehension check to screen test stimuli was
an effective means for controlling the confounding variable of vocabulary knowledge.
As discussed in the introduction, the presentation of the six tones in Cantonese on the
syllable /ji/ (Ching, 1984; Lui 2000) is not optimal. It is possible that children learned
the /ji/ stimuli as new words in the course of testing. In other words, they were effectively nonwords in the receptive lexicons of the test participants. The close proximity
of scores observed in Lui (2000) and the nonword stimuli in this study (0.66 vs. 0.73)
offers some support for this hypothesis.
The restriction in the number of tones tested to only three in the present study may
also have contributed to the high perception scores observed. This relates directly to the
number of items involved, reducing the attentional demands of the task.
In summary, the superior tone performance in this study implies that a methodology involving a reduced number of tones, a two-choice format and the use of words
within a child’s vocabulary inventory is well adapted to the test capacities of children
as young as 2;09.
4.2
Lexical versus nonlexical items in tone perception
Although there have been a few studies examining the effect of linguistic knowledge on
Cantonese tone processing, none of them have involved children. With the design of
word and nonword tokens in this study, the children’s superior performance on words
provides strong evidence that lexical knowledge facilitates tone perception, which agrees
with Lee, Vakoch, and Wurm (1996) but differs from Cutler and Chen (1997), who
imposed time constraints on participants for making responses. Tonal information is
hard to represent in working memory (Taft & Chen, 1992) and is auditorily coded in short
term memory (Lee, Vakoch, & Wurm, 1996). One possible explanation for the superior
response to words is that lexical information helps to code the rapidly fading tone information into long term memory. In the nonword response, no lexical information can be
used as a retrieval cue. Although, following Peynircioglu (1995), the nonword vowel /a/
was presented in the form of reduplicated syllables to assist short term memory, the
scores in the nonword condition were still much lower than those in the word condition.
One may speculate that young children do not treat tones separately from segmental
information, as an abstract representation (Taft & Chen, 1992). Instead, tone by itself
is treated as an aspect of the syllable as a whole and may consequently be difficult to
separate, indeed may be inseparable, from the segmental information and hence not
readily stored for future retrieval separate from a specific lexical carrier.
H owever, we need to interpret the superior scores on lexical over nonlexical items
with caution. The different outcomes from the two conditions might simply reflect
research design constraints. In the nonword environment, children were only permitted
two trials for learning the dolls’names. Some children may have had difficulty memorizing
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Tone perception ability of Cantonese-speaking children
the names in the time permitted. If this was the case then the results do not reflect
perception problems. In fact, it is interesting to note at this point that some of the children did indeed point to the incorrect doll while at the same time successfully imitating
the tone produced by the experimenter.
F urthermore, Barton (1980) noted that experimental tasks involving nonsense
syllables were too difficult for young children. It is thus not entirely clear to what extent
failures of task performance were due to task difficulty rather than tone perception
difficulty. It is possible that task problems of this nature could be addressed by increasing
the number of practice trials allowed, perhaps to the point where the children can name
the dolls spontaneously. Successful attempts at such training on children between 3
and 4.5 years have been reported by G raham and H ouse (1971) and Barton (1980).
Judging from the superior performance in the word condition and the related problems of utilizing nonwords, we believe that the former is a better choice in studying young
children’s tone perception ability, provided that the words used are in the child’s inventory.
4.3
The relative ease of identifying the three basic tones
The relative importance of pitch height and contour in tone perception as demonstrated
by G andour (1981; 1983) has been a major focus for researchers in the field. N evertheless,
no conclusive result can be arrived at based on studies of both the normal-hearing and
the hearing-impaired population (Ching, 1984; Ching, 1988; Fok, 1984; Lui, 2000;
Varley & So, 1995).
Applying the two dimensions in analyzing the three tone contrasts in this study
suggests that T1 / T4 and T2 / T4 should be easier than T1 / T2 as they differ from each
other both in terms of pitch height and contour. The prediction wa s only partially
supported, however. While children found T1 / T4 easy to perceive, the correct tone
identification on T2 / T4 was much lower.
The use of the generic terms pitch height and contour appears to be unsatisfactory in explaining the relative ease of tone identification. We therefore analyzed the
tones in terms of a more precise fundamental frequency measurement and put forward
the hypothesis that the greater the difference in fundamental frequency between the
two tones, the easier it would be for children to make correct identification. U nder this
hypothesis the relative ease of identifying T1/ T4 is understandable in view of the marked
discrepancies in pitch at both onset and offset. Performance comparable to that found
on T1/ T4 was noted on T1/ T2 identification. There is a significant difference in the value
of F 0 at onset on both tone contrasts — over 70 and 90 H z in speakers 1 and 2, respectively. The marked difference in F 0 onset may be the reason for the relative ease of
identification in the two tone contrasts. As for T2 / T4, scores are consistently lower
than those in the other two pairs. The values of F 0 at onset, unlike those for T1 / T4 and
T1 / T2 contra sts, are very similar. The difference is within 4 H z only across the two
speakers. The similarity in F 0 onset may result in decreased tone discriminability, which
is not diminished by subsequent changes in contour shape and offset differences.
Children’s overall performance on this task suggests that the similarity of F 0 at
onset has a more important impact on tone identification than that of F 0 at offset. The
role of differences in tone onset and offset in determining tone perception performance
merits further exploration.
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K. Y. S. Lee, S. N. Chiu, and C. A. van Hasselt
401
5 Conclusions
In this study, we have simplified the methodologies used for testing tone perception so
that the perception abilities of children as young as three years of age can be tested. This
has, in part, involved including a word comprehension test to exclude words that are
not in the child’s receptive vocabulary. By controlling for linguistic knowledge we were
able to deploy the time saved by not testing unfamiliar words on examining perception
of more tone pairs in the experimental setting.
Children were observed to be more successful at perceiving tones on words than
on nonwords. Although we are not entirely sure if the difference was due to the experimental design, we believe the inherent problems in using nonwords may unduly bias the
data. We, hence, suggest utilizing words as stimuli in further studies concerning young
children’s tone perception ability. The use of meaningful words instead of nonsense
syllables is also recommended for training items for learning Cantonese tone.
F inally, we found that children are equally successful at identifying contrasts
between T1 / T2 and T1 / T4, but have more difficulty on the T2/ T4 contrast. We propose
that the relative similarity of F 0 at onset is more important in predicting ease of perception of tone contrasts than is that of similar F 0 at offset. The hypothesis certainly needs
further verification in future research with larger sample sizes and with more tone
contrasts.
Received: March 6, 2001; revised: February 6, 2002, September 12, 2002, December 4,
2002; accepted: December 23, 2002
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Appendix 1
Item list in word stimuli
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405
Appendix 2
Item list in the comprehension check
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Appendix 3
The scores (number of correct responses/ number of trials) obtained by the 31 participants in this
study
Word
Participant
Nonword
T1 / T2
T1 / T4
T2 / T4
T1 /T2
T1 / T4
T2 / T4
1
15 / 15
15 / 15
15 / 15
5/5
3/5
3/ 5
2
15 / 15
15 / 15
15 / 15
5/5
5/5
5/ 5
3
21 / 25
25 / 25
22 / 25
3/5
4/5
5/ 5
4
13 / 15
15 / 15
15 / 15
5/5
5/5
5/ 5
5
16 / 20
16 / 20
11 / 20
1/5
5/5
4/ 5
6
15 / 15
14 / 15
14 / 15
2/5
3/5
5/ 5
7
25 / 25
25 / 25
13 / 15
5/5
5/5
5/ 5
8
20 / 20
15 / 15
4/5
5/5
5/5
5/ 5
9
15 / 15
14 / 15
5/5
1/5
2/5
3/ 5
10
11 / 15
5/ 15
4/5
4/5
2/5
5/ 5
11
29 / 35
15 / 15
9/ 10
5/5
5/5
2/ 5
12
12 / 15
14 / 15
11 / 15
0/5
4/5
3/ 5
13
20 / 20
20 / 20
15 / 20
4/5
5/5
2/ 5
14
15 / 15
15 / 15
14 / 15
2/5
4/5
4/ 5
15
14 / 15
15 / 15
15 / 15
4/5
3/5
2/ 5
16
9 / 15
13 / 15
10 / 15
5/5
5/5
0/ 5
17
14 / 15
13 / 15
15 / 15
4/5
3/5
0/ 5
18
19 / 20
17 / 20
14 / 15
3/5
4/5
2/ 5
19
24 / 25
19 / 20
19 / 20
5/5
1/5
2/ 5
20
20 / 20
20 / 20
19 / 20
5/5
5/5
5/ 5
21
18 / 20
17 / 20
3/5
4/5
5/5
4/ 5
22
20 / 20
18 / 20
5/5
3/5
5/5
3/ 5
23
20 / 20
18 / 20
20 / 20
5/5
5/5
5/ 5
24
20 / 20
15 / 20
18 / 20
5/5
2/5
0/ 5
25
19 / 20
17 / 20
17 / 20
3/5
3/5
2/ 5
26
20 / 20
16 / 20
16 / 20
4/5
3/5
3/ 5
27
20 / 20
18 / 20
10 / 20
5/5
5/5
5/ 5
28
20 / 20
19 / 20
20 / 20
5/5
5/5
5/ 5
29
20 / 20
20 / 20
17 / 20
4/5
3/5
4/ 5
30
18 / 20
–
4/5
4/5
5/5
2/ 5
31
20 / 20
19 / 20
–
1/5
2/5
1/ 5
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