The Effect of Kana Literacy Acquisition on the Speech Segmentation Unit Used by Japanese Young Children

Journal of Experimental Child Psychology 75, 70 –91 (2000) Article ID jecp.1999.2523, available online at http://www.idealibrary.com on

The Effect of Kana Literacy Acquisition on the Speech Segmentation Unit Used by Japanese Young Children Kayoko Inagaki Chiba University, Chiba, Japan

Giyoo Hatano Keio University, Tokyo, Japan

and Takashi Otake Dokkyo University, Soka, Japan Three experiments were undertaken to investigate whether young children’s segmentation units would change as they learned to read kana letters, which represent morae (subsyllabic rhythmic units). The first 2 experiments used a vocal–motor segmentation task to examine whether 4- to 6-year-olds preferred to segment spoken words containing the special syllables CVN, CVQ, or CV: into syllables or into morae. The third experiment used a target monitoring task for CVN to examine whether children’s detection of the target syllable in a series of words would vary depending on the moraic constitution of the target and the moraic–syllabic status of the word initial in which the target was embedded. Results indicated that the children’s conscious segmentation of words, except for those having a geminate stop consonant (CVQ), developed from being a mixture of syllable- and mora-based to being predominantly mora-based as they learned to read kana letters. The tendency toward mora-based segmentation was also found in the target monitoring task, which required segmentation at a less conscious level. © 2000 Academic Press Key Words: speech segmentation; literacy; mora; syllable; Japanese preschoolers.

It has been demonstrated that people listening to their native language use a speech segmentation procedure that is language specific and related to its rhythm (Cutler, Mehler, Norris, & Segui, 1986). For example, French speakers listening This study was supported by the Human Frontier Science Program. We thank Jacques Mehler, the principal investigator of the project, for his valuable suggestions, and Kiyoko Yoneyama, Yoshie Kanai, and Hiroko Kondo for having served as experimenters. Address correspondence and reprint requests to Kayoko Inagaki, Faculty of Education, Chiba University, Yayo-cho, Inage-ku, Chiba-shi, Chiba 263-8522, Japan. 70 0022-0965/00 $35.00 Copyright © 2000 by Academic Press All rights of reproduction in any form reserved.

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to French, the rhythm of which is syllable timing, use a syllabic segmentation procedure (Mehler, Dommergues, Frauenfelder, & Segui, 1981), whereas English speakers listening to English, which is stress-based, use a procedure corresponding with its stress timing rhythm (Cutler & Norris, 1988). It is known that in the Japanese language a mora is the most important phonological unit (e.g., Kubozono, 1989). The mora is a subsyllabic unit, which may be a vocalic nucleus, a nucleus preceded by a syllable onset, the postvocalic portion of a syllable (e.g., a coda), or an extended portion of the vowel. Several recent psycholinguistic experiments have shown that native speakers of Japanese segment their speech using morae as the basic units. For example, Otake, Hatano, Cutler, and Mehler (1993), performing target monitoring experiments with college students as participants, found that a CV target (e.g., ta) was recognized in words beginning with a CV initial (e.g., tanishi) or CVN initial (e.g., tanshi) more readily than a CVN target (e.g., tan) was. Finding a CVN target (e.g., tan) in words starting with a CVNV initial (e.g., tanishi) was extremely hard. In other words, the CVN initial embedded in the first two morae was very difficult to recognize. Cutler and Otake (1994) also found, using phoneme detection experiments, that Japanese listeners produced faster and more accurate responses to moraic than to nonmoraic targets. Because the postvocalic portion of a syllable (e.g., the nasal coda represented by N) constitutes a moraic unit, it is not tightly connected to the vocalic nucleus, whereas the syllable onset cannot readily be separated because it is always coupled with the following nucleus to constitute a mora. It should be noted that efficient perception as well as smooth production of Japanese speech relies on the approximately equal duration of morae, not of syllables. Moreover, a group of similar words (e.g., otori, ootori, and ottori) can be clearly distinguished based on the duration of the same phoneme. Also, if the nasal coda in tenoto, which is a nonsense word, is prolonged, the word is taken as teNnoto (Otake & Yoneyama, 1994). Therefore, for Japanese speech, the mora-based segmentation procedure works much better than the syllable-based and other segmentation procedures, though, as will be explained later, most morae constitute syllables in Japanese. Is the use of this mora-based segmentation procedure attributable only to the purely phonological factor of the Japanese language-specific rhythm? Or is it, at least in part, a product of its writing system? This is a debatable issue. On the one hand, many studies have revealed that the acquisition and use of a particular writing system influences phonological awareness, that is, the ability to detect and manipulate the finer phonological units in a prescribed way (e.g., Ehri, 1993; Ehri & Wilce, 1980; Morais, Bertelson, Cary, & Algeria, 1986; Stanovich, Cunningham, & Cramer, 1984). A speech segmentation procedure or a preferred way of segmenting speech to identify words is not the same as the ability to detect and manipulate the phonological units of words. For example, adult French speakers can segment a word into phonemes while using the syllable-

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based segmentation procedure for recognizing words in speech. Nevertheless, it is possible that the acquisition and use of a particular writing system also influences speech segmentation procedures, especially the use of finer basic units. Japanese people have learned and used kana letters in combination with kanji (Chinese characters). Although kana is called a syllabary, each kana letter represents a mora more or less regularly. Therefore, the mora-based segmentation strategy used by Japanese adults may be a product of their literacy. Generally speaking, it is possible that increased experience in reading and writing changes the preferred segmentation procedure used by native speakers, including the basic unit of speech segmentation. On the other hand, several studies have shown that the speech segmentation procedure is fixed early in development and is highly inflexible. Even infants are sensitive to the rhythm of the language spoken by the people around them (Mehler et al., 1988). It is likely that children develop a segmentation procedure adapted to their native language long before they learn to read and write, as they acquire a variety of words and represent them. Several researchers have recently emphasized that both advanced phonological awareness and readiness to learn to read result from increased oral vocabularies, which require increasingly elaborate phonological representations of words to differentiate among them (Fowler, 1991; Goswami, in press; Metsala, 1999; Metsala & Walley, 1998; Walley, 1993). Moreover, even balanced bilingual speakers cannot easily switch segmentation procedures when they switch from one language to another (Cutler, Mehler, Norris, & Segui, 1992). Thus, it is possible that an individual’s speech segmentation procedure is not modified by later experiences, including those of reading and writing. One way to examine the effect of literacy on speech segmentation is to conduct experiments using illiterate adult speakers as participants, as was done by Morais and his associates (Morais, Bertelson, Cary, & Alegria, 1986; Morais, Cary, Alegria, & Bertelson, 1979). However, it is very hard to find such speakers in Japan. Although some second and later generation Japanese Brazilians could be tested (e.g., Otake & Yoneyama, 1998), their segmentation strategy may be influenced by their use of Portuguese, which has a syllable-based rhythm. An alternative way to test the effects of literacy is to perform experiments using preschool children who have not yet acquired kana literacy skills. We can examine whether or not these young children rely on the mora-based segmentation procedure and, if not, whether the acquisition of kana literacy skills is associated with the emergence of that procedure, though we cannot conclude from such developmental studies that the use of the kana writing system is a cause of the mora-based segmentation procedure. Thus, we have performed a series of experiments dealing with the effect of kana literacy acquisition on speech segmentation, using 4- to 6-year-old children before schooling as participants. Although there had been some preliminary studies on this issue (Inagaki & Hatano, 1992; Takahashi, 1996), the exact relationship between the level of

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kana literacy acquisition and the basic speech segmentation unit in Japanese was not known. We hope that the results reported below will shed light on the complex relationship between the acquisition of literacy and the basic segmentation unit in speech perception. Prior to this study there was little, if any, solid evidence (e.g., Morais, Content, Cary, Mehler, & Segui, 1989) for or against the influence of literacy acquisition on speech segmentation. The Kana Writing System Before the experimental data are offered, a brief explanation of the kana writing system is presented. Although the syllable and the mora are distinct conceptual units, many syllables in Japanese have just one mora each, which is represented by a single kana letter. Ordinary syllables, which occupy more than 70% of Japanese speech corpora (Otake, 1990), have either the CV or the V structure. Only five kinds of syllables, often called “special syllables,” have two morae, or a single mora with a phonological structure other than CV or V. These special syllables are represented by two or three kana letters and include (1) those having a nasal coda (CVN or VN); (2) those having a geminate stop consonant (CVQ or VQ); (3) those having a long vowel (or a quasi-double vowel), which has a length comparable to two morae (CV: or V:); (4) those having two preceding consonants (CCV), the second of which is usually a glide; and (5) various combinations of (1) to (4), most often that of (3) and (4). All except for (4) have two morae; (1) to (4) are represented by two kana letters, and (5), by three or more letters. The nasal code is represented by a single kana letter of the regular size, and a geminate stop consonant, a smaller letter. Long vowels are represented differently, but always by two kana letters. Therefore, reading and writing words that contain these special syllables may help children to differentiate between morae and syllables and to recognize morae as basic segmentation units. It is possible for us to infer what segmentation unit a child spontaneously uses by asking him or her to segment a word (or a fragment of speech) involving these special, multimoraic syllables in the absence of examples or corrective feedback. For example, if the mora is used, CVN will be divided into two units (CV and N), whereas if the syllable is the basic segmentation unit, CVN will be treated as a single unit. In the first two experiments we present here, we focused on these differences in the segmentation unit for the three special syllables CVN, CVQ, and CV:, and examined whether the segmentation unit would change as children acquired kana literacy. There were three possible outcomes: 1. The segmentation unit does not change: The segmentation based on morae is used even before the acquisition of kana literacy; thus kana literacy’s effect on the segmentation unit is negligible or merely strengthens a tendency that is already in place.

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2. The segmentation unit does change: from a mixture of mora-based and syllable-based to a mora-based one as children acquire kana literacy. 3. The segmentation unit does change: from syllable-based to mora-based as children acquire kana literacy. The first possibility is plausible if we assume that the speech segmentation procedure is autonomous. In contrast, the second and third possibilities can be derived from the assumption that literacy affects the segmentation procedure, more specifically, that the segmentation unit that is used in reading and writing becomes the basic one. The second and third possibilities differ only in terms of the initial segmentation procedure: The second takes into account the fact that morae and syllables often overlap in the Japanese language, as indicated above, and thus young children may not commit to using either of them exclusively, whereas the third considers syllables to be the most fundamental phonological unit (Mehler et al., 1981; Treiman & Zukowski, 1988). EXPERIMENT 1 We examined whether 4- to 6-year-old children who had acquired different levels of kana literacy would segment given words into morae or syllables. The experimental stimuli included six critical words, two each for three kinds of special syllables (CVN, CVQ, and CV:). Method Participants. Twenty-seven kindergarten children (14 boys, 13 girls), from predominantly lower-middle-class families, participated in the study. Japanese kindergartens, unlike those in the United States or other countries, are educational institutions for 3- to 6-year-olds. They are separated from elementary schools, and usually do not provide any systematic teaching of letters and numbers. The children’s mean age was 66 months and the range was 58 – 80 months. They were selected to represent four different levels of kana literacy acquisition. These levels were based on the criteria developed by the National Language Research Institute (1972), 1 and are defined as follows: Level 1, being able to read fewer than 20 of the 71 kana letters and none of the five kinds of special syllables; Level 2, being able to read 21–59 letters but none of the five kinds of special syllables; Level 3, being able to read one or two special syllables in addition to all 71 letters; and Level 4, being able to read all special syllables as well as all 71 letters. Each level was represented by 7 children, except for 1

Although the stages for kana reading acquisition established by the National Language Research Institute (1972) have been widely used in Japan, their definition of “special syllables” is a bit confusing and slightly different from the one we use in the present study. The five special syllables in their definition are CVQ, CV:, CCV, CCV:, and two particles that have two different pronunciations depending on their morphological status (Akita & Hatano, 1999). CVN is not included, probably because N is always represented by one character and its acquisition is easy.

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Level 4, which 1 child dropped out of. The mean age for Level 1 children was 62 months; for Level 2, 66 months; for Level 3, 65 months; and for Level 4, 74 months. Task and procedure. Children were individually tested in a small room in their kindergarten. They were given a vocal–motor word segmentation task (a “vocal– motor task” hereafter), a modified version of that used by Amano (1986) to assess children’s syllabic awareness. Children were presented words represented by drawings one at a time, and asked to make a doll jump on a series of different colored circles on paper while they articulated the given word (see Fig. 1). The task was designed to assess whether the children were using the syllable or the mora as their segmentation unit. First, the experimenter introduced two dolls, a Santa Claus and a Chinese boy doll, and said that the former was for herself and the latter was for the child. Then, she invited the child to play a word game and explained how to play it. “Let’s play a word game today. I will show you how to play it. [Showing the first card in the practice trials] What is drawn on this card? Yes, it is a kani (crab). I will make this Santa Claus doll jump and take steps ahead on these circles.” The experimenter jumped the doll two circles ahead, voicing, “ka/ni/,” and said, “Now, the doll went here, to the yellow circle. In this game, as you just saw, you are expected to make your doll go ahead as many circles as the word. Can you do that? Would you get your doll forward on the circles as Santa Claus doll did?” After one more demonstrated trial, the child was asked to perform two trials without demonstration by the following instruction: “Now, my Santa Claus doll will take a rest. So, would you make your doll jump alone?” When the child failed in any of these practice trials, the experimenter demonstrated the correct response, and asked the child to try once again. After the child succeeded consecutively in two trials without demonstration, he or she proceeded to the experimental trials, where the child was not given any feedback. Note that, although each child was shown how to move the doll and given corrective feedback if needed, the segmentation on these four practice trials did not give any clue as to whether a word should be divided into syllables or morae, because the demonstration and practice words consisted of ordinary syllables. Unlike in the conventional tasks measuring phonological awareness (Gombert, 1992), the child was not required to segment a word into the smallest units. The child was then given 15 words, 5 of which, like the practice items, included only regular CVs or Vs. Six of the remaining 10 words included 2 each for the 3 kinds of special syllables, for example, kureyon (yon constitutes a two-mora syllable) for CVN, rappa (rapp constitutes a two-mora syllable) for CVQ, or hiko:ki (ko: constitutes a two-mora syllable) for CV:. One word had three morae, and the other, four morae, for each special syllable. The other 4 words involved CCV (or CCV:), by which we could check whether children segmented words phonologically or in terms of kana letters. Examples of such words are kabocha (cha constitutes a one-mora syllable that is written in two

FIG. 1.

The vocal–motor segmentation task used in Experiment 1.

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kana) and kyu:ri (kyu: constitutes a two-mora syllable that is written in three kana). Data Analysis First, we classified children’s responses to each of the words containing the three special syllables, that is, a nasal coda (CVN or VN), a geminate stop consonant (CVQ or VQ), or a long vowel (CV: or V:), as to whether they demonstrated a syllable-unit or a mora-unit segmentation. For example, when the CVN word kureyon was segmented into ku/re/yon/, we classified it as syllableunit; ku/re/yo/n/was identified as mora-unit. Next, we identified the children’s segmentation pattern for each of the three special syllables. When both words for the same type of special syllable were segmented into syllable-units or moraunits, we classified that pattern as syllable-based or mora-based, respectively. When children’s segmentations were different for the two words involving the same special syllable, we classified it as undecided. We classified children’s segmentations of the words containing CCV or CCV: in terms of whether they were based on letters or not. As indicated above, the CCV constitutes one syllable that has one mora, but is written using two kana letters. Thus, for example, when kabocha (a pumpkin) was segmented into ka/bo/ch(i)/(y)a/, it was classified as a letter-based segmentation, while ka/bo/cha was a syllable- or mora-based segmentation. A letter-based segmentation for CCV or CCV: would suggest that such children’s apparently mora-based segmentation for words having the three kinds of special syllables (CVN, CVQ, or CV:) may have been based on kana letters and did not reflect the basic segmentation unit in speech perception. We hoped to confirm that this task could reveal children’s basic phonological segmentation strategy by showing that their segmentation for the CCV and CCV: words was not letter-based. Results and Discussion Table 1 shows the segmentation patterns for the three kinds of special syllables exhibited by children at the four different levels of kana literacy acquisition. The segmentation patterns for the words containing a nasal coda and a long vowel were similar to each other, and showed a shift in segmentation from a mixture of syllable- and mora-based units to mora-based units as literacy increased. Specifically, the children at Level 1 showed both syllable-based and mora-based patterns, while those at higher levels showed the mora-based pattern almost exclusively. The distributions of segmentation patterns (mora-based versus others) were significantly different between Level 1 and other levels by Fisher’s exact probability test (ps , .05). We also analyzed the relationship between the kana literacy acquisition levels and the use of the mora-based segmentation procedure, partialing out the effect of age. We ran ANCOVAs for the number of mora-unit responses among the levels (Level 1 vs Levels 2– 4), with the children’s chronological age (CA) as a covariate. We found that the main effect of

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INAGAKI, HATANO, AND OTAKE TABLE 1 Segmentation Patterns for Three Kinds of Special Syllables (Experiment 1)

Types of special syllables Nasal coda (CVN or VN)

Geminate stop consonant (CVQ or VQ)

Long vowel (CV: or V:)

Segmentation patterns

Level 1 (N 5 7)

Level 2 (N 5 7)

Level 3 (N 5 7)

Level 4 (N 5 6)

Mora-based Syllable-based Undecided

4 1 2

6 0 1

7 0 0

6 0 0

Mora-based Syllable-based Undecided Mora-based Syllable-based Undecided

1 4 2 4 1 2

2 4 1 7 0 0

0 7 0 7 0 0

2 2 2 6 0 0

Note. Mora-based means mora-unit segmentation for both items; syllable-based, syllable-unit segmentation for both items; undecided, one mora-unit and one syllable-unit segmentation.

the kana acquisition level was statistically significant for CV:, F(1, 24) 5 6.97, p , .05, and nearly significant for CVN, F(1, 24) 5 3.69, p , .10. The contribution of CA was small within the range of our participants and far from significant. In contrast, for the segmentation of words containing a geminate stop consonant (CVQ or VQ) the children at Levels 1 and 2 of kana literacy showed both syllable-based and mora-based patterns, while the children at Level 3 predominantly showed syllable-based patterns, although the tendency among children at Level 4 was not clear. This result may be an artifact due to the nature of the task requiring vocal–motor correspondence, because it was difficult for a child to move the doll in correspondence with the pause that the geminate stop consonant had on the second mora. As shown in Table 1, there were a substantial number of “undecided” responses (12.3%), partly because the children’s segmentation strategies may have been affected by factors such as word length (whether comprising three or four morae) and the position of the special syllable in the word (whether appearing at the initial, middle, or ending of the word). Therefore, a better controlled set of stimulus words was used in Experiment 2. For the CCV and CCV: words, no letter-based segmentation was found. Thus, this vocal–motor segmentation task was appropriate to assess the phonological unit that children use in segmenting a word or a fragment of speech. In sum, children’s segmentation of words containing a nasal coda or long vowel seems to change from being a mixture of syllable-based and mora-based to being predominantly mora-based, as children acquire kana literacy skills, not as they grow older.

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EXPERIMENT 2 Although the result of Experiment 1 was suggestive, it was not conclusive, mainly because the Level 1 children were small in number and because different segmentation units were sometimes adopted for two different words containing the same kind of special syllable. Thus, we performed a second experiment using many more Level 1 children and better controlled word choices. We also examined, after this segmentation task, whether children could switch their segmentation unit from a syllable to a mora, when they were guided. Method Participants. Fifty-two children (27 boys, 25 girls; mean age 66 months, range 54 –78 months) participated. The children were selected to represent four different levels of kana literacy acquisition, based on criteria developed by the National Language Research Institute (1972), as in Experiment 1. Twenty-two children were at Level 1 (mean age 64 months), 10 at Level 2 (66), 10 at Level 3 (67), and 10 at Level 4 (69). They were recruited from three day care centers within Tokyo and in its suburbs, and were mostly from lower-middle-class families. They had had no systematic teaching of reading kana letters. Task and procedure. Children were individually given two tasks: a vocal– motor segmentation task and a segmentation-switching task (a “switching task” hereafter). This vocal–motor task included three words each for the three special syllables (CVN, CVQ, and CV:) to reduce the number of “undecided” cases in identifying children’s patterns for each type of special syllable. Moreover, the word length was controlled: each word contained four kana letters and four morae, but three syllables. Where the multimoraic syllable appeared in the word was varied systematically. After four practice items, the children were given 20 words. Of these, 9 were critical words involving one of the special syllables, 5 contained only regular CVs or Vs, and the remaining 6 contained CCV (or CCV:) syllables. Frog and rabbit dolls were used instead of the Santa Claus and Chinese boy dolls used in Experiment 1. After finishing the vocal–motor task, some of the same children were given the switching task. This was to examine whether those children who had adopted the syllable-based segmentation procedure in the optional vocal–motor task could use the mora-based one when they were guided, in other words, whether they preferred the syllable as the segmentation unit even though they could divide a given word into subsyllabic units of morae. The experimenter demonstrated a moraic segmentation to the child who had used a syllable unit in the preceding vocal–motor task, for the first word from each of the three types of special syllables, and then asked the child to segment the same word in the same way as the experimenter did. “Now, it’s my doll’s turn. This time my frog doll will jump somewhat differently. Watch carefully. After my frog doll jumps, I would like your rabbit doll to jump in the same way

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as the frog did.” If the child had segmented, for example, the word so:jiki (cleaner) based on the syllable unit (so:/ji/ki) in the previous vocal–motor task, the experimenter demonstrated the segmentation based on the mora unit; that is, she made the frog doll go four circles ahead, voicing, “so/:/ji/ki.” Then she asked, “Do you understand how the frog doll got ahead? Now, will you make your rabbit doll go ahead as the frog did just now?” When the child succeeded in imitating the experimenter’s moraic segmentation, he or she was asked to segment the second and the third words in the same way without the experimenter’s demonstration. When the child failed for the first word, the experimenter demonstrated the moraic segmentation for the second word, and asked the child to segment it in the same way. Irrespective of the success or failure for the second word, the child was then asked to segment the third word independently. Data Analyses Vocal–motor task. As in Experiment 1, we classified children’s responses to each of the words containing the three types of special syllables (i.e., CVN, CVQ, and CV:) into the syllable-unit or mora-unit segmentation, and then we identified their segmentation pattern for each of the three special syllables. When two of the three or all three words containing the same type of special syllable were segmented into syllable-units or mora-units, it was classified as a syllable-based pattern or mora-based pattern, respectively. As in Experiment 1, children’s segmentations of CCV and CCV: were classified in terms of whether they were letter-based or not. Switching task. Children’s responses were coded for each special syllable with respect to whether they succeeded in adopting the mora-based segmentation, following the demonstration by the experimenter for a preceding word. Results and Discussion Table 2 shows the children’s segmentation patterns for each type of the special syllables at each level of kana literacy acquisition. Figures in the square brackets show the segmentation patterns used by the Level 1 children who could not read kana letters at all. For the words having a nasal coda and a long vowel, it was clear that a considerable proportion of the Level 1 children based their segmentation on syllables; especially those who could not read at all showed segmentation on syllables and morae with equal frequencies. In contrast, the children at higher levels in kana literacy acquisition showed predominantly mora-based patterns. The differences in the proportion of the mora-based patterns between Level 1 and Levels 2– 4 were significant by Fisher’s exact test ( ps , .05). Two of the Level 4 children who had acquired complete kana literacy showed a letter-based pattern for the CCV and CCV: words; thus their patterns for words having a nasal coda or a long vowel should also be judged as letter-based patterns rather than mora-based ones. The developmental patterns strongly suggest that the word segmentation unit is influenced by the acquisition of kana literacy.

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KANA LITERACY AND SPEECH SEGMENTATION TABLE 2 Segmentation Patterns for Three Kinds of Special Syllables (Experiment 2)

Types of special syllables Nasal coda (CVN or VN) Geminate stop consonant (CVQ or VQ) Long vowel (CV: or V:)

Segmentation patterns

Level 1 (N 5 22)

Level 2 (N 5 10)

Level 3 (N 5 10)

Level 4 (N 5 10)

Mora-based Syllable-based

16 [6] 6 [5]

9 1

10 0

10 0

Mora-based Syllable-based Mora-based Syllable-based

11 [4] 11 [7] 13 [5] 9 [6]

7 3 8 2

2 8 9 1

2 8 9 1

Note. Mora-based means two or more mora-unit segmentations of the three; syllable-based means two or more syllable-unit segmentations of the three. Figures in the square brackets show the number of segmentation patterns by 11 Level 1 children who could not read any kana letters.

The segmentation of the words containing a geminate stop consonant showed a different developmental pattern, as was also found in Experiment 1. The children at lower levels of kana literacy showed both syllable-based and morabased patterns, whereas those at higher levels showed predominantly syllablebased patterns, though there were a few who relied on the mora-based segmentation. Two of the Level 4 children were judged as using the letter-based segmentation strategy, for the reason described above. In sum, the results for the vocal–motor task in Experiment 2 replicated those of Experiment 1. Children’s segmentation of words, except for those having a geminate stop consonant, appears to develop from a mixture of syllable-based and mora-based to a predominantly mora-based as they learn to read kana letters. This strongly suggests that the second possibility offered in the Introduction is most plausible. Although the length of the words was controlled in this experiment, the consistency of responses to the same kind of special syllable was not quite high, except for children with higher levels of kana literacy acquisition. There were 28 cases in which responses to the same kind of special syllable were split (26.4%), but only 1 such case occurred among the Level 3 and 4 children. There were 18 cases of split responses among the Level 1 children and 9 among the Level 2. Because we did not systematically vary the familiarity or neighborhood density of the target words, we cannot examine the effects of these variables that have been suggested by emergentists (Metsala & Walley, 1998). However, our informal observation suggests that a majority of the inconsistent responses seemed to be due to the varied position of the special syllable. For instance, all 12 children who showed one syllable-unit segmentation for a geminate stop consonant did so to the word that included CVQ in the word initial, whereas all 5 children who showed one mora-unit response did so to either of the two words that included CVQ in the middle. This probably occurred because these children tended to

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TABLE 3 Proportions of Children Who Succeeded in Changing from Their Syllable-Unit Segmentation to the Mora-Unit One for the Test Word (without Demonstration) on the Switch Task (Experiment 2)

Special syllables Nasal coda Geminate stop consonant Long vowel

Level 1 (N 5 22)

Levels 2–4 (N 5 30)

4/6 2/9 3/9

1/1 12/17 4/4

Note. The denominator shows the number of children who segmented the first word based on a syllable-unit, and the numerator, the number of children who succeeded in changing their segmentation unit to the mora for the test word without experimenter’s demonstration.

segment each word into units of equal duration once such a unit was established for the initial syllable, which consisted of a single mora. Table 3 shows the percentages of children who succeeded in segmenting based on the mora-unit themselves (after being shown the mora-unit segmentation by the experimenter for the first word or the first and second words, but not for the target word). Here we grouped children of Levels 2– 4 together. These children could almost always segment words involving special syllables into morae when instructed. In contrast, about 30% of the Level 1 children (7/22 and 5/22, respectively) failed to divide words containing a geminate stop consonant or a long vowel, though almost all of them showed at least one mora-unit segmentation for the nasal coda. In other words, for some Level 1 children the vocal– motor task may have assessed their phonological awareness, not their preferred segmentation unit. To summarize, Experiment 2 as well as Experiment 1 showed that children’s segmentation of words, except for those having a geminate stop consonant, develops from being a mixture of syllable-based and mora-based to being predominantly mora-based, as they learn to read kana letters. Before learning many kana letters, some children segment words into morae, and others, into syllables. Many of the children who do not use a mora-based segmentation procedure can divide words into morae when instructed. This finding suggests that there may be some de´calage between the ability to segment words into morae and the use of the mora as the basic segmentation unit. Although we were interested in assessing whether children would divide a fragment of speech into syllables or morae, the vocal–motor segmentation task required them explicitly to divide a word, and this may have amplified the effect of literacy on the basic segmentation unit (Gombert, 1992; Goswami, in press). We thus conducted Experiment 3 to examine whether the learning of kana letters would influence the speech segmentation unit even when we assessed it in an implicit, less conscious way.

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EXPERIMENT 3 This experiment was undertaken to examine the effect of literacy on the speech segmentation unit at a less conscious level for children 4 – 6 years of age. The task was a slightly modified version of the syllable monitoring task used by Otake et al. (1993), adapted for young children. A target, either CV (e.g., ki) or CVN (kin), was given auditorily, and the participating child was asked to detect the target in a sequence of words. It was hypothesized that, if the child segmented a word into syllables, finding the target in a word starting with the same syllable as the target (e.g., target ki for word kinoji and target kin for word kinji) would be easier than doing so in a word starting with a different syllable from the target (ki for kinji and kin for kinoji), as was shown for French speakers who relied on the syllable-based segmentation (Mehler et al., 1981). In contrast, if the child segmented a word into morae, finding the single-unit target (e.g., ki) would be easier than the double-unit target (kin) in both types of words (kinji and kinoji), and recognizing the latter (kin) in a word in which it was embedded in the first two morae (kinoji) would be particularly hard, as shown for adult Japanese speakers (Otake et al., 1993). We chose the nasal coda as the target in this experiment, because previous studies (e.g., Otake et al., 1993) had shown clearly that Japanese adults use the mora-based segmentation procedure for the nasal coda. If children’s performance differed, we could conclude that some shift in segmentation occurs as children acquire kana literacy skills. Moreover, holding in working memory CVN as well as CV as the target seems easier for children than holding the target with a geminate consonant (CVQ) or a long vowel (CV:). Our pilot study indicated that young children could detect the kin target in the kinoji-type words at a much higher rate than the college students in Otake et al. (1993), who showed a strikingly high miss rate of more than 60%, though it had been explained to them in detail with a few examples that a CVNVCV word (e.g., tanishi) included the CVN target (tan). However, the young children may have responded to any words starting with CV, even when the given target was CVN. Therefore, in addition to CVNVCV words, CVNCV words, and irrelevant words that did not start with ki, the children were given distractors starting with ki that was followed by other phonemes than a nasal coda (e.g., kiyoji), so that we could examine whether they responded to any kiCV word, representing the kin target as just ki. Method Participants. Forty-seven children (31 boys, 16 girls; mean age 64 months, range 44 –70 months) participated. They were selected to represent the four levels of kana literacy acquisition, which were based on the criteria developed by the National Language Research Institute (1972), as in Experiments 1 and 2. We tested 10 additional children (5 Level 1, 2 Level 2, and 3 Level 3 children), but

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because they could not complete the task, their data were excluded. Overall, 14 children were at Level 1 (mean age 63 months), 11 at Level 2 (64), 11 at Level 3 (63), and 11 at Level 4 (65). They were recruited from two kindergartens within Tokyo and its suburbs, and were mostly from lower-middle-class families. We also experimented with 20 undergraduate students so that we could compare performances of children who had just acquired kana literacy with those of adults, who had much experience of using kana letters, with essentially the same procedure. Since these college students were recruited from the same university as in Otake et al. (1993), their data would serve as the bridge between the present children’s results and the previous adults’ ones. Task and procedure. This task required children to recognize the target syllable in a sequence of two or three words. The target syllable and test words, both of which had been tape-recorded, were given auditorily. For the CV target (e.g., ki), the sequence of words included a CVNVCV word (e.g., kinoji), a CVNCV word (kinji), or neither, and for the CVN target (e.g., kin), a CVNVCV word (e.g., kinoji), a CVNCV word (kinji), or a distractor (e.g., kiyoji). The CV targets were ki, sa, mi, and ka; the CVN targets had an n after them. CVNCV words were kinji, sanji, minji, and kanji; CVNVCV words had the vowel o after the n; the corresponding CVCVCV (or CVCVV) words that were distractors of the CVN targets were kiyoji, sakio, misao, and karota. All these words were familiar given names for boys in Japanese or sounded like such names. We also added “-chan” at the end of each word (e.g., kinji-chan), as Japanese speakers often do when they address a child. Each target was presented three times: The CV target was followed by a sequence of two to three words that included a CVNCV word, a CVNVCV word, or neither, and the CVN target was followed by a sequence of two to three words that included a CVNCV word, a CVNVCV word, or a distractor. Therefore, these were 24 test trials consisting of the target and a sequence of words. For 16 test trials the words containing the target appeared four times as the first in the sequence, four times as the third, and eight times as the second, and the remaining 8 test trials included distractors or irrelevant words. The procedure of the experiment was as follows. Each child was told that if a stimulus word contained a target sound (e.g., ta) at the beginning of word (e.g., takeo), the child was to beat a toy tambourine. Before the experiment, the child was given six practice trials with other targets, for two of which the following sequence of words did not include the word containing the target (e.g., hideji, ikuo, and toyoki as the sequence of words for sa as the target). For these practice trials, the child was given corrective feedback with a short explanation when needed. For example, “You had to find a name starting with hi. So you should have beaten the tambourine as soon as you heard hirota-chan because it started with hi” or “So you should not have beaten because subaru-chan did not start with hi.” The experimenter proceeded to the next trials without repeating the trials that the child had failed. After these six practice trials, the child was moved

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to the main trials, with the experimenter announcing, “Let’s move on to the main task.” For the college students the targets and the word sequences were presented over headphones from a DAT recorder, and they were asked to press a response key instead of beating a tambourine. The output from this recorder was fed to a second DAT recorder, which also recorded a pulse triggered by the student’s response. Data analyses. We counted the number of hits (correctly beating the tambourine or pressing a key for the word containing the target syllable) for each participant and for each pair of target and word types. We also counted the number of false detection responses (beating the tambourine or pressing a key for the word not containing the target) for the sequences of all irrelevant words and those including distractors. We measured children’s reaction times from the audiotapes. The duration from the beginning of the word containing the target to the tambourine beat was recorded using a stopwatch. Two independent measurements by the same coder showed high correlation (r 5 .99) across all trials. For the college students, the intervals between onset of the target word and response pulse were measured by a computer-operated device. Individual reaction times were calculated for each target/word type condition by averaging the measured durations for trials for which the participant responded correctly. We excluded from reaction time analysis the data from children who responded correctly on no or only one trial for any of the four conditions. There were two such cases at Level 1, three at Levels 2 and 4, and four at Level 3. For the college students no data were excluded, because the missing rate in the CVN target/CVNVCV word condition was so high. Results and Discussion The percentages of true or false detection for each target/word type condition are shown separately for the children at four different kana reading levels and the college students in Table 4, and the mean reaction times, in Table 5. We first examine the results for the college students in comparison with those of Experiment 3 in Otake et al. (1993). As shown in Table 4, the miss rate for CVN targets with CVNVCV words was extremely high, even higher than that observed by Otake et al. (1993). This means that without prior detailed explanation, ordinary native speakers of Japanese do not recognize the CVN target in CVNVCV words. For the other three target-word conditions, the miss rates were uniformly low, as in the previous study. The mean reaction times for these three conditions were generally longer in this experiment, which was probably due to the inclusion of sequences consisting of all irrelevant words and those with a distractor. However, the college students’ patterns were similar to those obtained in the Otake et al. study: CV targets had shorter reaction times for both CVNVCV words and CVNCV words than CVN targets had for CVNCV words, though CV target– CVNCV word conditions had slightly longer reaction times than expected. The

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TABLE 4 Percentages of True or False Detection for Each Target/Word Type Condition (Experiment 3) CV (Ki) Target words (examples) Level 1 Level 2 Level 3 Level 4 Adults

[N [N [N [N [N

5 5 5 5 5

14] 11] 11] 11] 20]

CVN (Kin)

CVNVCV (kinoji)

CVNCV (kinji)

Neither (masuo)

CVNVCV (kinoji)

CVNCV (kinji)

Distractors (kiyoji)

91.1 63.6 84.0 86.4 98.8

89.3 81.8 90.9 93.2 98.8

1.8 2.3 0.0 0.0 0.0

73.2 72.7 61.4 65.9 1.3

87.5 81.8 90.9 100 95.0

67.9 50.0 40.9 36.4 8.7

Note. False detections are for the CV target/neither word type and for the CVN target/distractors word type, and true detections are for the remaining target/word types.

magnitude of the difference was similar to that observed in Otake et al. (1993), that is, about 50 ms between the fastest and slowest condition. Taking into account the methodological differences, especially the lack of the detailed explanation that CVNVCV words include the CVN target, the present results for college students seem compatible with those of Otake et al. (1993). Unlike the college students, the children in the present study showed generally low and roughly comparable rates of misses across conditions (see Table 4). That is, they often detected the CVN target in CVNVCV words. However, they also responded very often to distractors. The percentage of false recognition of the CVN target for distractors was not significantly different from that of true detection for CVNVCV words among the Level 1 children. However, they

TABLE 5 Mean Reaction Times for Each Target/Word Type Condition (Experiment 3) CV (Ki) Target words (examples) Level 1 Level 2 Level 3 Level 4 Adults

[N [N [N [N [N

5 5 5 5 5

12] 8] 7] 8] 20]

CVN (Kin)

CVNVCV (kinoji)

CVNCV (kinji)

CVNVCV (kinoji)

CVNCV (kinji)

1.36 (0.32) 1.31 (0.20) 1.37 (0.28) 1.10 (0.28) 0.83 (0.23)

1.23 (0.23) 1.44 (0.29) 1.27 (0.35) 1.19 (0.33) 0.86 (0.27)

1.13 (0.20) 1.41 (0.49) 1.23 (0.23) 1.09 (0.32) —

1.44 (0.41) 1.50 (0.24) 1.39 (0.20) 1.19 (0.24) 0.88 (0.24)

Note. Figures in parentheses are SDs. Because almost all the adults failed to recognize the target, CVN, in CVNVCV words, the reaction time could not be measured in the CVN target/CVNVCV word condition.

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seldom responded to irrelevant words (in the CV target–neither word conditions). This implies that the children tended to respond on the partial match between the target and corresponding words. We thus ran separate 2 (target: CV, CVN) 3 2 (word: CVNVCV, CVNCV) ANCOVAs for each of the four levels of kana literacy acquisition, with the number of false recognition responses to distractors as a covariate. In other words, in these analyses we discounted children’s true detection responses by their tendency to respond based on the partial match. A significant main effect of word types was found, F(1, 9) 5 15.60, p , .01 for Level 3 and F(1, 9) 5 31.54, p , .001 for Level 4, indicating that targets were easier to detect (more correct numbers of hits) in CVNCV words (e.g., kanji). Also a significant main effect of target types was found, F(1, 9) 5 5.73, p , .05 for Level 3 and F(1, 9) 5 5.81, p , .05 for Level 4, indicating that CV targets were easier to detect. Moreover, a significant interaction effect was found, F(1, 9) 5 14.76, p , .01, for Level 4. These results were all primarily due to the (disproportionate) difficulty of the CVN target/CVNVCV word condition, which is a major characteristic of the mora-based segmentation pattern. Assuming that the children at higher reading levels segmented speech into morae, we had expected that finding the single-unit target (e.g., ki) would generally be easier than finding the double-unit target (kin), but this was not supported. This may have been due to the children’s tendency to respond based on the partial match and/or their uniformly high detection rates. We can conclude that children at Levels 3 and 4 seemed to be approaching the adult pattern of mora effect. In contrast, even Level 1 children who had just begun to learn to read kana letters did not reveal any clear syllable effect in this target monitoring task. The pattern of mean reaction times for target/word type conditions for children (Table 5) must be interpreted with caution, because the number of participants at each reading acquisition level was even smaller, and because short reaction times may have been produced by responding based on the partial match. Separate 2 (target) 3 2 (word) ANOVAs for each level revealed that only three effects were significant: the interaction effect at Level 1, F(1, 11) 5 19.90, p , .01, and at Level 3, F(1, 6) 5 7.78, p , .05, and the main effect of word type at Level 4, F(1, 7) 5 5.65, p , .05. The mora effect in reaction times that had been observed for adults in Otake et al. (1993), that is, equivalently faster detection of the CV target for both CVNVCV and CVNCV words than of the CVN target for the CVNCV word, was not found, even among the Level 4 children. Both of these significant effects were, we think, primarily due to the shorter reaction time for the CVN target/CVNVCV word condition, which probably implies that impulsive rather than reflective children recognized the target in this condition. To summarize, whereas the Level 1 children, who had just begun to learn to read kana, did not reveal any clear syllable effect in this target monitoring task, the children at Levels 3 and 4, who had almost finished learning to read kana letters, revealed some mora effect. However, the latter children’s responses were

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still different from the adult patterns in that (a) they could detect CVN targets in CVNVCV words much better than the college students, and (b) their recognition of CV targets in CVNCV words was not as fast as in CVNVCV words nor faster than their recognition of CVN targets in CVNCV words. Having increased experience of using kana letters may make the postvocalic portion of a syllable more readily separable and, at the same time, make the syllable onset less readily dissociable. As a whole, in light of the above results, the second possibility offered in the Introduction, that is, from the mixture of the syllable-based and mora-based segmentation to the exclusive use of the mora-based segmentation, seems most tenable. GENERAL DISCUSSION AND CONCLUSION The first two experiments, using the vocal–motor task, indicated that speech segmentation of Japanese was based on both the mora and the syllable when the children were at the lowest reading level, and the performance of these children in the third experiment, using the target monitoring task which assessed the effect of literacy in less conscious way, was consistent with this characterization. In contrast, all three experiments showed that segmentation was based predominantly on the mora among the children at the two highest reading levels. The intermediate children were, we assume, at a transitional stage with not quite stable mora-based segmentation. Interestingly, the shift to the mora-based segmentation was associated more strongly with the kana reading level than with the chronological age. However, the target monitoring experiment showed that even the children who had almost finished learning to read kana letters detected the CVN target in CVNVCV words much more easily than did the college students who had had much experience using kana letters. This was probably because the adult speakers of Japanese could not readily divide morae, which they had been accustomed to treating as basic units, into the onset and the vocalic nucleus. A plausible, and our preferred, interpretation of these results is that Japanese speech segmentation is influenced by the acquisition and use of kana literacy. There is a plausible alternative interpretation. It indicates that the development of a mora-based segmentation is dependent on the amount of experience one has in the phonological processing of Japanese. More specifically, the mora-based segmentation of speech is attributable only to the phonological factor of the Japanese language-specific rhythm. Since the mora and syllable overlap to a considerable extent, some young children may rely, at least in part, on syllables in segmentation. When children become phonologically mature enough to rely exclusively on the mora as the basic unit, their learning of kana letters can be facilitated, because kana letters are moraic. These two interpretations are not mutually exclusive, however. A number of studies have shown that, because kana letters represent morae, learning to read some of them enhances children’s moraic awareness, which in turn makes it

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easier for them to learn to read other kana letters (Akita & Hatano, 1999). Moraic awareness and the moraic segmentation strategy are conceptually very different, because the former denotes the ability to segment a given word into morae as required, which is closely related to how the word is represented in the mental lexicon (Metsala, 1999), and the latter is the preferred reliance on morae as basic units in prelexical processing. Nevertheless, it seems reasonable to assume that there are also mutually enhancing relationships between the moraic segmentation strategy and learning to read kana letters. Although the general picture of developmental changes in the basic segmentation unit seems clear, it should be noted that details varied from experiment to experiment, and also among the three types of special syllables in the first two experiments. It is possible that the effect of literacy on speech segmentation may vary depending on whether a task assesses the conscious, offline articulation unit or the online speech segmentation unit without conscious control (Gombert, 1992; Goswami, in press). Each task also has its own limitation; for example, it may be hard to give a unit to a geminate stop consonant in the vocal–motor task. We must examine our various tools for measuring segmentation unit in detail, by applying them to the same participants. How much can we generalize the present finding demonstrating the relationship between the acquisition of literacy and the basic segmentation unit in speech perception? More specifically, are these two related also in other languages that have different rhythms from mora timing, and in other orthographies differing in degrees of the regularity of the script–sound correspondence? We speculate that the acquisition of literacy reinforces, if not changes, the basic speech segmentation unit, as long as a given rhythm of language is somehow represented in orthography. For example, the fact that a group of scripts is pronounced differently depending on whether it has a stress (e.g., re in recognize versus in recall) is likely to make English speakers aware of its stress timing rhythm. With regard to the generalization to other types of scripts, we can derive an answer by analogy from the previous studies on the development of phonological awareness in a variety of scripts. These studies have revealed that (a) children develop the ability to detect and manipulate the finer phonological units that are mapped to orthographic units; those who learn morphograms or syllabaries develop phonemic awareness more slowly than those who learn alphabets (Huang & Hanley, 1995; Mann, 1986); (b) the regularity of the script–sound correspondence enhances this development (Cossu, Shankweiler, Liberman, Katz, & Tola, 1988; Goswami, Porpodas, & Wheelwright, 1997; Wimmer, Landerl, Linortner, & Hummer, 1991); and (c) this ability can be transferred to another language they learn (Durgunoglu, Nagy, & Hancin-Bhatt, 1993; Durugunoglu & Verhoeven, 1998; Geva, Wade-Woolley, & Shany, 1993). It is highly likely that the speech segmentation unit is affected by learning to read and write, though such effects may be harder to detect in some cases than in others.

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