Glottometrics 8, 2004, 1-11

Are the effects of vowel repetition influenced by frequencies?
A corpus study on CVCVCV-structured nouns with andwithout vowel repetition
Katsuo Tamaoka, Hiroshima University, Japan1
Shogo Makioka, Osaka Women’s University, Japan
Tadao Murata, Kyushu Institute of Technology, Japan
Abstract. A psychological study by Tamaoka and Murata (2001) suggested that CVCVCV-structured nonwords (e.g., /kohomo/) with the same vowel repeated showed longer naming latencies than the same-structured
nonwords without vowel repetition (e.g., /kohami/). One of the possible factors for prolonging vowel repetition
could be the frequency of vowel repetition in Japanese. Thus, the present study calculated token frequencies fornouns with the same vowel repeated within a CVCVCV phonological structure, based on the Japanese lexical
corpus (287,792,797 words) of Amano and Kondo (2000). The results showed that vowels were repeated among
Japanese nouns with a CVCVCV string more frequently than the random possibility of 4 percent. In addition,nouns with the same vowels in the first and second positions (i.e., V1 and V2 in the CV1CV2CV3) showedsignificantly higher occurrences than the random chance of 20 percent, whereas nouns with the same vowels inthe second and third positions appeared at the random level (i.e., V2 and V3). Since it is expected that higher
frequency enhances speed and accuracy in naming, phonological structures with the same vowel repeated can be
expected to be more quickly and accurately named. Conflicting results between the present corpus study and theexperimental study by Tamaoka and Murata (2001) excluded the possibility of the frequency of vowel repetition
affecting the speed and accuracy of phonological processing.

Keywords: vowel repetition, phonological structure, corpus study, Japanese nouns

1. Introduction
A study by Tamaoka and Murata (2001) suggested that CVCVCV-structured nonwords with thesame vowel repeated like /kohomo/ showed longer naming latencies than the same-structured
nonwords without vowel repetition like /kohami/. The explanation proposed for this is the‘whack-a-mole’ phenomenon. The vowel in the first CV mora (C referring to ‘consonant’ and V‘vowel’) continues to have a high activation level even when the following CV morae are activated. When the same vowel is repeated throughout the CV morae, all the CV morae will besimultaneously excited to reach the activation level. To avoid confusing the continuous order of
the CV mora string, sequential morae must be inhibited so as not to be activated to the same
degree as the previous CV mora. This pattern of excitation and inhibition results in the decreased
speed of phonological processing for nonwords. As for naming nonwords with no repeated vow1

Address correspondence to: Katsuo Tamaoka, International Student Center, Hiroshima University, 1-1, 1-Chome,
Higashihiroshima, Japan 739-8524. E-mail: ktamaoka@hiroshima-u.ac.jp

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K. Tamaoka, S. Makioka, T. Murata

els, the processing of sequential order of the CV mora string is not affected by other morae. Thus,
nonwords with varying vowels are named more quickly than nonwords which repeat vowels and,concomitantly, fewer errors are observed among nonwords with non-repeated vowels.
While the ‘whack-a-mole’ phenomenon was a psychological explanation, some linguists
provide a different explanation from a phonological perspective. The Obligatory Contour Principle (OCP) refers to a linguistic constraint on similar or same phonological features from being
repeated (e.g., Fukazawa, 2000; Ito & Mester, 1986; Kubozono, 1999; Kubozono & Ota, 1998;
Leben, 1973; McCarthy 1986; Yip, 1988). Kubozono and Ota (1998) suggested the possibility
that vowel dissimilation in Japanese may be a result of the OCP. For example, the two Japanesemorphemes /nana/ (‘seven’) and /ka/ (‘day’) combine to form the compound word /nanoka/ (‘theseventh day’) instead of /nanaka/, which would seem to be the likely combination. This process ofvowel dissimilation occurs so as to avoid vowel repetition of /a/ in sequence within the three mora
CVCVCV word structure. Thus, it would be expected that naming visually-presented Japanesewords and nonwords which violate the OCP (i.e., same vowel repetition in a series of CV strings)
would result in slower processing speeds and higher error rates. Yet, the linguistic explanation of
OCP does not conflict with the psychological explanation of the ‘whack-a-mole’ phenomenon.
Despite these psychological and linguistic explanations, ‘frequency of vowel repetition’ inJapanese could be a possible factor for prolonging vowel repetition. Therefore, the present study
calculated type and token frequencies for nouns with the same vowel repeated within a CVCVCV
phonological structure, based on the Japanese lexical corpus (287,792,797 words) of Amano andKondo (2000). Study 1 examined the same vowels in all three consecutive V positions and Study
2 in two consecutive V positions. Both Studies 1 and 2 were used to examine whether the rate ofvowel repetition in CVCVCV-structured Japanese nouns appears to be significantly greater or
lesser than the random chance rate of occurrence.

2. Conditions for calculating word frequency
Three conditions were established for calculating word frequency. First, the random chance rateof occurrence was established using only CVCVCV-structured words. Under this condition, thepossibility of a 3-mora CVCVCV-structured word, which contains the same vowel in threeconsecutive positions, is calculated as 4 percent (with the 5 different Japanese vowels of /a/, /e/, /i/,/o/ and /u/ in three positions calculated as 1/53×5 = 1/52). In the same way, the possibility of thesewords with the same vowel in chosen two positions in their CVCVCV structure is 20 percent(with the 5 different vowels in two chosen positions calculated as 1/(5×5) × 5 = 1/5, the thirdvowel may be arbitrary).
Secondly, only nouns were selected from the word corpus of Amano and Kondo (2000),
which still served as sufficient data for the purpose of the present investigation. As Japanese verbs
and adjectives have grammatical inflections, they were not included in the present corpus study.
For example, the Japanese verb /ugoku/, meaning ‘to move’, inflects as in /ugoka(nai)/,/ugoki(masu)/, /ugoku(toki)/, /ugoke(ba)/ and /ugokoR/. It uses all the five Japanese vowels of /a/,/i/, /u/, /e/ and /o/ in its grammatical inflections.
Thirdly, both frequencies of type and token were used for the purpose of this study. In type
frequency, a single word is only counted once, regardless of how many times it is repeated in thewritten text. On the other hand, in token frequency (i.e., accumulative word frequency) a word iscounted every time it appears in the text. Since a rare word (e.g., /guNzoR/ meaning ‘ultramarine’) has the same type frequency of 1 as a frequently used word (e.g., /daigaku/ meaning

Are the effects of vowel repetition influenced by frequencies?

3‘university’), the present study considered token frequency as a better indicator of word frequency.

3. STUDY #1: Frequency of CVCVCV-structured nouns with the same vowels occurringin three consecutive vowel positions
Study 1 examined the occurrence of the same vowels in three consecutive V positions within
CVCVCV-structured nouns. In this study, all nouns with a CV1CV2CV3 structure had to share thesame vowel in all V1, V2 and V3 positions.

3.1. Lexical Corpus and Selection Procedure
As a result of the word frequency index created by Amano and Kondo (2000) from their study on
accumulative word frequency (i.e., token frequency), a very large lexical corpus of 341,771
words was established from newspapers containing 287,792,797 words of accumulate frequency.
All these words were taken from the Asahi Newspaper printed from 1985 to 1998. This is one of
the largest and the most up-to-date word corpora created from calculating frequency of words inJapanese written texts. The present study utilized this corpus to investigate nouns with vowel
repetition.
The programming language of MacJPerl 5.15r4J for Macintosh was used to run a calculation
procedure. For Study 1, only nouns with a CVCVCV phonological structure were used. Thus,
three mora nouns with VCVCV, CVVCV, CVCVV, VCVV, or VVV strings were not included.
Therefore, the Japanese special long vowel /R/1, where the same vowel appears twice without
having a consonant between them, was not counted. In the same way, double vowels such as /ai/,/oi/, /ue/ were also excluded from the count. Other special sounds such as the nasal /N/ and thegeminate /Q/ were also excluded as well as contrasted sounds such as /kya/, /myo/, /pyo/.

3.2. Results
Study 1 used two types of frequencies: type and token frequency. Type frequency only counts aword once and then is calculated by a simple addition of each word’s frequency of ‘1’ (ΣNi), eventhough a word may appear repeatedly in a printed text. Token frequency, on the other hand, iscalculated by taking the number of times each word appears in the text and adding all thesefrequencies together (ΣWf). The present study took the .01 level of significance to reject thestatistical null hypothesis, since the word corpus used was very large. These two frequency
indexes of type and token frequency are reported separately as listed below.

3.2.1. Type Frequency
As shown in Table 1, among the five Japanese vowels, the vowel /a/ was the most frequently
repeated in three consecutive positions, found in 674 nouns or 61.50 percent of the total 1,096
nouns (both general and proper nouns) with vowel repetition. The second most frequently usedvowel was /o/ found in 204 different nouns or 18.61 percent of the total nouns counted.

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K. Tamaoka, S. Makioka, T. Murata

Ranking third was the vowel /i/, repeated in 158 different nouns or 14.42 percent of the total
nouns counted. The vowel /u/ came in forth, repeated in 57 nouns or 5.20 percent of all nouns
counted. The least repeated vowel was /e/, repeated in only 3 different nouns or 0.27 percent of allnouns counted. Kubozono (1999) explained that the three vowels of /a/, /i/ and /u/ are mostfrequently found within the various languages of the world. It is therefore reasonable to expectthat these vowels will be repeated more often in a single noun in Japanese than the vowel /e/.
Since the vowel /o/ is ranked at the top of the ‘sound hierarchy’ (Murata, 1984, 1990; Tamaoka &Murata, 1999), /o/ tended to be repeated more than the vowel /e/, although both these vowels havepoints of articulation within the middle of the vowel space. This tendency was observed in bothgeneral and proper nouns in the same way.
Table 1Same Vowels in Three Consecutive V Positions
Word Frequency (∑Ni)
Vowels General Nouns
Proper Nouns
/a/
197
477
/i/
118
40
/u/
25
32
/e/
2
1
/o/
51
153
Total
393
703 *
Grand Total
8,142
10,348Ratio
4.83%
6.79% H

Accumulative Word Frequency (∑Wf)
Total General Nouns
Proper Nouns
Total
674
166,823
113,351
280,174
158
36,6201,664
38,284
57
4,710
5,364
10,074
3
136
11
147
204
183,961
13,832
197,793
1,096 *
392,250 *
134,222 *526,472 *
18,4904,664,720
1,090,679
5,755,399
5.93% H
8.41% H12.31% H
9.15% H

Note 1 : * p <.01.
Note 2 : The random possibility of 3-mora CVCVCV nouns which have the same vowels in three consecutive V
positions is 4 percent.
Note 3 : The sign H refers to the frequency of nouns with vowel repetition which is significantly higher thanrandom chance (4.00%).
Note 4 : The grand total of 18,490 refers to the total number of nouns with a CVCVCV phonological structure outof the 341,771 nouns taken from the word corpus of Amano and Kondo (2000).
Note 5 : The grand total of 5,755,399 refers to the total accumulative word frequency for the 18,490 nouns with a
CVCVCV phonological structure.

The frequency of nouns with vowel repetition appearing in Japanese written texts was examined using Chebysheff’s inequality theorem (see Maezono, 2002; Matsubara, Nawata & Nakai,
1994; Suzuki, 1999). The calculation of probability is provided by:
P(|X - m| < kσ) > 1 - 1/k2
where the m is a mean of a scattered variable X and sigma (σ) is a standard deviation2. Using thismeasurement, 393 nouns (4.83%) were found to contain the same repeated vowels from among
8,142 general nouns with a CVCVCV structure, which fell within the range of the random chanceof occurrence (326 times or 4.00%) at the .01 level of significance. In contrast, 703 nouns(6.79%) were found to have the same vowels repeated among 10,348 proper nouns, which was
sigificantly higher than the 4 percent chance of random occurrence. A total of 1,096 nouns(5.93%) out of 18,490 repeated the same vowel in the CVCVCV phonological strings. This noun
frequency was significant at the probability level of 1 percent. In short, type frequency indicatedthat the assimilation constraint causing vowel repetition in nouns with a CVCVCV phonologicalAre the effects of vowel repetition influenced by frequencies?

5

structure which was observed in the total number of proper nouns and the total number of bothgeneral and proper nouns together, but not in the total number of general nouns alone.

3.2.2. Token frequency
As discussed in the introduction of this paper, accumulative word frequency or token frequency is
considered to be more accurate in indicating occurrence of words than type frequency. Similar totype frequency, token frequency also showed a similar pattern in terms of vowels repeated inthree consecutive positions. As shown in Table 1, these vowels are listed in the Japanese vowel
kana order of /a/, /i/, /u/, /e/ and /o/ in all the categories of general nouns, proper nouns and thetotal of both.
An interesting tendency observed in token frequency is a high accumulative frequency ofoccurrence of Japanese nouns with vowel repetition. Although type frequency of general nouns
did not show a significantly high occurrence of words with vowel repetition, token frequency inthe category of general nouns was calculated as 392,250 (8.41%) out of the total of 4,664,720.
According to Chebysheff’s inequality theorem, this figure of token frequency was significantly
higher (p < .01) than the random chance of occurrence of 4 percent. Therefore, these nouns withvowel repetition in three consecutive positions are often seen in written texts. For the category ofproper nouns, type frequency was 134,222 (12.31%) out of 1,090,679, which was significantly
higher than the random chance of occurrence (p < .01). The grand total of 526,472 (9.15%) out of
5,755,399 also showed significantly high occurrence of nouns with same vowel repetition (p< .01).

3.3. Discussion
Study 1 examined the existent to which the same vowels were repeated three times within a
CVCVCV phonological structure in a corpus of Japanese nouns. Although type frequency ofgeneral nouns did not show significantly high occurrences of same vowel repetition, token
frequency indicated significantly high repetition. Since type frequency only counts a word once,
regardless of how often it is used, the index of token frequencies reflects actual appearance in
written Japanese texts. Therefore, Study 1 concluded that vowels were repeated among Japanesegeneral and proper nouns with a phonological CVCVCV string far more frequently (i.e., 9.15%)
than the random chance level of four percent.

4. STUDY #2: Frequency of CVCVCV-structured nouns with the same vowel occurringin two consecutive vowel positions
Study 2 investigated the frequency of nouns with the same vowel occurring in two consecutive V
positions within a CV1CV2CV3 string. In this case, a vowel could be repeated in either of two
ways: (1) V1 and V2 or (2) V2 and V3. The same vowels found in V1 and V3 were not considered
to be in consecutive positions, so they were only considered for their frequency of occurrence
which was used simply for comparing the other two conditions of (1) and (2). Results would thenbe expected to display either a lesser or a greater degree of word frequency than the random
chance rate of occurrence of 20 percent among CVCVCV-structured Japanese nouns.

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K. Tamaoka, S. Makioka, T. Murata

4.1. Lexical Corpus and Procedure
Study 2 made use of the same lexical corpus as in Study 1.

4.2. Results
The number of Japanese nouns having the same vowel in two consecutive positions is shown in
Table 2. Words with the same vowel in three consecutive positions discussed in Study 1 are notincluded in the detail counts of each vowel in Table 2. For determining the significance level of
one percent, counts of three-consecutive-vowel repetitions were included. According to the totalsof both type and token frequencies, the type of vowel found in two consecutive positions among
CV1CV2CV3-structured nouns was similar to the vowel found in the order of three consecutive
positions, with the most frequently-repeated vowel being /a/ and the least frequently-repeatedvowel being /e/.

4.2.1. Type frequency
General nouns with the same vowel in the V1 and V2 positions were counted 1,664 times(20.44%) out of 8,142 general nouns. Likewise, proper nouns showed a similar count of 2,138
times (20.66%) out of 10,348 proper nouns. The total of both types of nouns together indicated apercentage of 20.56 or a count of 3,802 times out of 18,490 nouns. Once frequency counts of thesame vowel in three consecutive positions were included, the figures become 2,057 (25.26%) for
general nouns, 2,841 (27.45%) for proper nouns and 4,898 (26.49%) for both together. As
indicated by the upper arrow in Table 2, all these figures were significantly higher than the
random chance rate of occurrence of 20 percent based upon the calculation from Chebysheff’s
inequality theorem (p < .01). Therefore, it is concluded that nouns with the same vowels in thefirst and second V positions of a CVCVCV phonological string occur more frequently than random chance.
Type frequency of general nouns which have the same vowel in the V2 and V3 positions was
13.68 percent or 1,114 times out of 8,142 general nouns. Including the same vowel in three consecutive positions, type frequency became 18.51 percent or 1,507 times. According to the calculation based on Chebysheff’s inequality theorem, this frequency of occurrence did not significantly differ from the 20 percent random chance rate. Similarly, same vowel occurrence in V2
and V3 positions among proper nouns was 18.86 percent or 1.952 times (12.07 percent or 1,249
times excluding the same vowel in thee consecutive positions) out of 10,348 proper nouns, which
did not significantly differ from the random chance level. The total of both general and proper
nouns occurring 18.71 percent or 3,459 times (12.78 percent or 2,363 times without the samevowel in three consecutive positions) out of 18,490 nouns did not show a significantly lower orhigher frequency than the random chance level. Therefore, the same vowel in the second andthird positions within CVCVCV strings occurs at the random chance.
Although the V1 and V3 positions of a CV1CV2CV3 string were not considered to be consecutive, type frequency was counted as a basis for comparison. General nouns with the samevowels in the first and third positions of a CVCVCV string were counted 1,740 times or 21.37
percent (1,347 times or 16.54 percent without the same vowel in the three consecutive positions)out of 8,142 general nouns. This frequency of occurrence was the same as the random chance.
However, proper nouns with such vowel repetitions appeared 2,548 times or 24.62 percent (1,845

Are the effects of vowel repetition influenced by frequencies?

7

times or 17.83 percent without the same vowel in three consecutive positions) out of 10,348
proper nouns, which was significantly higher than the random chance rate of occurrence of 20
percent (p < .01). The total of both general and proper nouns with this type of vowel repetition
showed a frequency of 23.19 percent or 4,288 times (17.26 percent or 3,192 times without thesame vowel in three consecutive positions) out of 18,490 general and proper nouns. This figure
was at the random chance rate of occurrence.

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K. Tamaoka, S. Makioka, T. Murata

These results suggest that the vowels occur frequently in the first and second V positions of
CVCVCV string, but occur at the random chance level in the second and third V positions. The
frequency of nouns with the same vowels in the first and third V positions seems to fall between
the two previous conditions. Among general nouns the frequency was equal to the random chance,
among proper nouns there were significantly high occurrences, but both together the frequency
returns to the random chance level.

4.2.2. Token Frequency

Token frequency of Japanese nouns with the same vowels in two consecutive positions was also
examined and these figures were considered more representative of the natural occurrence of
these nouns than those of type frequency.
General nouns with the same vowel in V1 and V2 positions of a CV1CV2CV3 string werecounted 1,729,112 times or 37.07 percent (1,336,862 times or 28.66 percent without the samevowel in three consecutive positions) out of 4,664,720 general nouns. Based upon the calculationof Chebysheff’s inequality theorem, this count was significantly higher than the random chance
rate of occurrence of 20 percent (p < .01). Proper nouns showed a relatively high frequency rateof 387,383 times or 35.52 percent (23.21 percent or 253,161 times without the same vowel inthree consecutive positions) out of 1,090,679 proper nouns. This token frequency rate was alsosignificantly higher than random chance (p < .01). The total of both general and proper nouns
indicated a high frequency rate of 36.77 percent or 2,116,495 times (27.63 percent or 1,590,023
times without the same vowel in three consecutive positions) out of 5,755,399 general and proper
nouns, which was significantly higher than random chance (p < .01). Overall, token frequency ofthe same vowels in V1 and V2 positions in nouns with a CV1CV2CV3 structure indicated significantly higher occurrences than the random chance rate of 20 percent. Therefore, it is concluded that these nouns appear more frequently than just by random chance.
Token frequency of general nouns, which had the same vowel in the V2 and V3 positions of
its CV1CV2CV3 phonological string, was 21.64 percent or 4,664,720 times (13.23 percent or
617,369 times without the same vowel in three consecutive positions) out of 4,664,720 general
nouns. This frequency of occurrence was at the random chance level of 20 percent. Similarly, thesame vowel occurring in the second and third V positions among proper nouns was 23.99 percent
or 261,673 times (11.69 percent or 127,451 times without the same vowel in three consecutive
positions) out of 1,090,679 proper nouns, which was at the random chance level. The total frequency of both general and proper nouns was, naturally, at the random chance level, being counted 22.09 percent or 1,271,292 times (12.94 percent or 744,820 times without the same vowel inthree consecutive positions) out of a total of 5,755,399 of both nouns together. Therefore, thesame vowels occur at the random chance level in the second and third V positions of a CVCVCV
string.
Token frequency of nouns with the same vowel in V1 and V3 positions of a CV1CV2CV3
string was counted as a basis for comparison. General nouns with the same vowel in the first andthird V positions were counted 1,025,462 times or 21.98 percent (633,212 times or 13.57 percent
without the same vowel in three consecutive positions) out of 4,664,720 general nouns. This
token frequency figure for general nouns was at the random chance level. In contrast, proper
nouns with the same vowel in the first and third V positions appeared 346,198 times or 31.74
percent (211,976 times or 19.44 percent without the same vowel in three consecutive positions)out of 1,090,679 proper nouns, which was significantly higher than the 20 percent random chance

Are the effects of vowel repetition influenced by frequencies?

9rate of occurrence. However, the total token frequency among both general and proper nouns was
1,371,660 times or 23.83 percent (845,188 times or 14.69 percent without the same vowel in threeconsecutive positions) out of 5,755,399 both types of nouns together. This figure was at the random chance level.

4.3. Discussion
Study 2 examined the rate of occurrence of nouns with the same vowels found in two consecutive
V positions within their CVCVCV strings. As shown in Table 2, type and token frequencies
showed a general trend that the same vowels were found more frequently than at the random
chance level in the first and second V positions of CVCVCV-structured nouns, but basicallyoccur at the random chance level in the second and third V positions and in the first and third V
positions, excluding proper nouns of the first and third V positions.

5. General Discussion

The present study proved that the same vowels in the three consecutive V positions of CVCVCV
strings of nouns are more frequently repeated than the random possibility of 4 percent in bothcases of type and token frequencies. Furthermore, the same vowels occurring in two consecutive
or determined V positions were also observed in type and token frequencies of CVCVCV-structured nouns. In the two consecutive or determined positions, the random chance level was 20
percent. The same vowels in the first and second V positions of CVCVCV string of nouns occur
more frequently than the random chance level. On the other hand, both type and token frequency
were found to be at the random chance rate of occurrence for nouns with the same vowels repeated in the second and third V positions in their CVCVCV strings. Accordingly,
CVCVCV-structured nouns with the same vowels in the first and second V positions occur more
frequently than random probability, whereas same vowels in the second and third V positions
occur at the rate of random chance. The same vowel repetition of the first and third positions,though not consecutive but determined positions, showed mixed results; the random chance level
among the general nouns, but significantly higher than the random chance level among the proper
nouns. However, when both the general and proper nouns were examined together, it returned to
the random chance level.
As depicted in Figure 1, an interesting trend was found when combining the results of token
frequency concerning nouns with the same vowels in three consecutive and two consecutive or
determined V positions (see also Tables 1 and 2). The percentage of nouns with the same vowels
in three consecutive V positions overlaps with the percentage of nouns with the same vowels in
two positions. In other words, the percentages of nouns with the same vowels in V1 and V2, V2
and V3, and V1 and V3 positions all include the same percentage of nouns with the same vowels
in V1, V2 and V3 positions (i.e., 9.15%). Therefore, when 9.15 percent was subtracted from all
total percentages of each condition of the same vowels in two V positions, the results were 27.63
percent for V1 and V2 positions, 12.94 percent for V2 and V3 positions, and 14.69 percent for V1
and V3 positions.
Figure 1 uses ‘H’ to refer to a frequency of occurrence that is greater than random chance.
Thus, according to the boxes with the arrow H, it can be seen that nouns with the same vowels
occurring in V1 and V2 positions, as well as in V1, V2 and V3 positions with a CV1CV2CV3

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K. Tamaoka, S. Makioka, T. Murata

structure, have a total token frequency of 36.77 percent. This suggests that once the same vowels
occur in V1 and V2 positions, they are likely to be repeated in the V3 position (i.e., 9.15% for V1 =V2 = V3).
In summary, the findings of the corpus study indicated that vowels were repeated among
Japanese nouns with a CVCVCV string more frequently than the random possibility of 4 percent.
In addition, nouns with the same vowels in the first and second positions (i.e., V1 and V2 in the
CV1CV2CV3) showed significantly higher occurrences than the random chance of 20 percent,whereas nouns with the same vowels in the second and third positions appeared at the random
chance level (i.e., V2 and V3). Since higher frequency enhances speed and accuracy in naming,
phonological structures with the same vowel repeated can be expected to be more quickly andaccurately named. However, Tamaoka and Murata (2001) found in their experimental study thatnative Japanese speakers named CVCVCV-structured phonemic strings with same vowel
repetition less quickly and less accurately than unrepeated ones. This finding conflicts with theresults of the present corpus study and excludes the possibility of the frequency of vowel
repetition affecting the speed and accuracy of phonological processing.

36.77%

V1=V2=V3

22.09%

H V1=V2

H

27.63%

9.15%

V2=V3
12.94%

23.83%

V1=V3
14.69%

Figure 1 . Token frequency of Japanese nouns with vowel repetition
Note 1 : A V1, V2 and V3 refers to vowels in a CV1CV2CV3 string.
Note 2 : Percentages in Italics are the calculated frequencies of nouns
out of the grand total of 5,755,399 CVCVCV-structured nouns.
Note 3 : Percentages underlined indicate token frequency of thatparticular box plus the token frequency of nouns with the samevowels in V1=V2=V3.

Notes
1

The pronunciation of words in this paper is transcribed using Japanese phonemic symbols whichindicate three special sounds in Japanese: /N/ for nasal, /Q/ for geminate and /R/ for long vowel.

Are the effects of vowel repetition influenced by frequencies?

112

The cutoff points at the 1 percent significant level for a type frequency of CVCVCV-structured general
nouns is calculated as follows. The type frequency is 8,142 (see Table 1). A random probability is given by
1/53 (three positions within five changeable vowels) ×5 (five different vowels) which equals 1/25. Thus,
the mean m of the variable X becomes 326 (m = 8,142×1/25 = 325.68). The standard deviation σ is given
by m multiplied by 24/25 and squared by one half, σ = (8,142×1/25×24/25)1/2 = 17.68. The probability at
the 1 percent level of significance was established by 1 - 1/k2 = 0.99. Thus, the value k was calculated as
10. Substituting all the values, the formula becomes P(|X - 326| < 10×17.68). After calculating this, theresult was P(149 < X < 503) > 0.99. Since the actual type frequency is 393, this figure is within the rangeof 149 to 503. Consequently, the frequency 393 falls into a random chance range at the 1 percent level ofsignificance. This calculation procedure is applied to all other frequencies in Studies 1 and 2.

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