David Roberts Independent

Ginger Boyd

Johannes Merz

Valentin Vydrin

N Bienvenue Sambiéni

Quantifying written ambiguities in tone languages: A comparative study of Elip, Mbelime, and Eastern Dan

Whether tone should be represented in writing, and if so how much, is one of the most formidable challenges facing those developing orthographies for tone languages. Various researchers have attempted to quantify the level of written ambiguity in a language if tone is not marked, but these contributions are not easily comparable because they use different measurement criteria. This article presents a first attempt to develop a standardized instrument and evaluate its potential. The method is exemplified using four narrative texts translated into Elip, Mbelime, and Eastern Dan. It lists all distinct written word forms that are homographs if tone is not marked, discarding repeated words, homophony, and polysemy, as well as pairs that never share the same syntactic slot. It treats lexical and grammatical tone separately, while acknowledging that these two functions often coincide. The results show that the level of written ambiguity in Elip is weighted towards the grammar, while in Mbelime many ambiguities occur at the point where lexical and grammatical tone coincide. As for Eastern Dan, with its profusion of nominal and verbal minimal pairs, not to mention pronouns, case markers, predicative markers, and other parts of speech, the level of written ambiguity if tone is not marked is by far the highest of the three languages. The article ends with some suggestions of how the methodology might be refined, by reporting some experimental data that provide only limited proof of the need to mark tone fully, and by describing how full tone marking has survived recent spelling reforms in all three languages.

1. Introduction 1 When tone is not marked fully2 in the orthography of a tone language, written ambiguities inevitably occur. But since no orthography succeeds in eliminating ambiguity entirely, how can an orthography developer judge what constitutes an acceptable level of under-representation? To help answer this question this paper compares tonal written ambiguities in the orthographies of three Niger-Congo languages: Elip (Bantu A62, Cameroon), Mbelime (Gur, Benin), and Eastern Dan (Mande, Côte d'Ivoire).

Since written ambiguity is closely related to the concept of functional load, it will help to provide a definition of this term at the outset. King's (1967a:190) definition is probably the most frequently cited:

The term functional load is customarily used in linguistics to describe the extent and degree of contrast between linguistic units, usually phonemes. In its simplest expression, functional load is a measure of the number of minimal pairs which can be found for a given opposition. More generally, in phonology, it is a measure of the work which two phonemes (or a distinctive feature) do in keeping utterances apart -in other words a gauge of the frequency with which two phonemes contrast in all possible environments.

One of the aims of the analysis presented in this chapter is to demonstrate that it is perfectly valid to address the issue of functional load "in its simplest expression", by presenting lists of tonal minimal pairs. But our analysis goes three steps further than this. It seeks to establish whether the tonal ambiguities, if tone is not marked orthographically in a given language, are weighted towards the lexicon or the grammar. It also systematizes the relationships between the various grammatical ambiguities, paying particular attention to tonal inflection in the verb system. Finally, it proposes a straightforward way for orthography developers to quantify tonal written ambiguities with a view to standardizing procedures and thus enabling cross-linguistic comparison.

Functional load

2.1 Literature overview A brief summary of the rest of the literature on functional load will help set the scene. The term can be traced back to the Prague School [START_REF] Mathesius | La structure phonologique du lexique du tchèque moderne[END_REF][START_REF] Mathesius | Zum Problem der Belastungs-und kombinationsfähigkeit der Phoneme[END_REF][START_REF] Trubetzkoy | Grundzüge der Phonologie[END_REF]), but it was [START_REF] Martinet | Economie des changements phonétiques: Traité de phonologie diachronique[END_REF] who brought it to prominence among Western linguists.3 Early researchers tended to be concerned with functional load as it related to diachronic sound change (Hockett 1966;King 1967b;[START_REF] Wang | The measurement of functional load[END_REF], but others applied it to language acquisition [START_REF] Brown | Functional load and the teaching of pronunciation[END_REF][START_REF] Brown | Functional load and the teaching of pronunciation[END_REF][START_REF] Catford | Phonetics and the teaching of pronunciation: A systemic description of English phonology[END_REF]Ingram 1989;[START_REF] Pye | A comparison of initial consonant acquisition in English and Quiché[END_REF]) and dialect comparison (Kies 1986). Early researchers also embarked on a quest for a viable method of quantifying functional load in corpus-based evaluations including Danish [START_REF] Rischel | On functional load in phonemics[END_REF], Russian and Czech (Kučera 1963), Romanian [START_REF] Avram | Some thoughts on the functional yield of phonemic oppositions[END_REF], Germanic (King 1967a), Santa Clara Tewa and -closest to the concerns of our own study -Yoruba, Igbo, and Hausa (Greenberg 1959).

However, these early attempts at quantification were largely unsuccessful, and for many years inquiry into functional load fell completely out of fashion. It is only with the advent of computational linguistics that quantification has finally become possible (e.g., Kitahara & Shigeaki 2000;Wedel et al. 2013a;Wedel et al. 2013b). Several studies investigate tone languages [START_REF] Surendran | The functional load of tone in Mandarin is as high as that of vowels[END_REF][START_REF] Stokes | Articulatory complexity, ambient frequency and functional load as predictors of consonant development in children[END_REF][START_REF] Munro | The functional load principle in ESL pronunciation instruction: An exploratory study[END_REF][START_REF] Surendran | Quantifying the functional load of phonemic oppositions, distinctive features, and suprasegmentals[END_REF][START_REF] Oh | Crosslanguage comparison of functional load for vowels, consonants, and tones[END_REF]) and some include African languages [START_REF] Pellegrino | Functional load and the structure of vowel systems[END_REF][START_REF] Melick | Tone in the Mbelime verb system[END_REF][START_REF] Coupé | Functional load and organization scales in phonological systems[END_REF]).

Functional load and orthography development

What is perhaps less well known is that, throughout this period, researchers developing orthographies for previously unwritten minority languages have always found the concept of functional load to be intuitively reasonable, and frequently evoke it to articulate their ideas (Powlison 1968:79-80, 86-91;Gudschinsky 1970;Gordon 1986:75-78;Cahill 2001:16, 19-20). It is also common for researchers to make passing references to the functional load of tone in individual African languages:

[…] the functional load carried by tone [in Akan] is more frequent at the level of grammar than at the lexical level. (Abena 1985, as cited in Koffi 1994:4)⁴

In the Grassfields languages the functional load of tone is so important that it would be unreasonable to ignore tone completely. (Mfonyam 1990:23) It has been shown that since tone has a high functional load in the [Bura] language it should not be left to the discretion of the reader, it has to be indicated in writing. (Badejo 1989:49) Tone has a heavier or lighter functional load according to the intensity with which it is used to make minimal distinctions of meaning. […] Even if tone has a very light functional load […] (e.g. Lingala), it is still a tone language […]. (Kutsch Lojenga 1993:5) ⁴We have been unable to locate the published version of this article; this citation appears on page 4 of a manuscript version. Unfortunately, Abena (1985) is not listed in the references. Vol. 14, 2020 Statements of this kind are not necessarily unhelpful. After many years of fieldwork, an experienced linguist is in a stronger position than anyone to make an informed judgment about whether tone carries a heavy or light functional load. But it should be recognized that no objective comparison between the above four statements is possible because they are only impressionistic.

Language Documentation & Conservation

Occasionally, researchers do undertake numerical counts. [START_REF] Burmeister | Tone orthography in Tano languages[END_REF]2) reports that, in Anyi Sanvi (Kwa, Côte d'Ivoire), tonal minimal pairs account for 1% of the words in a lexicon of 5,000+ entries. Bird (1999a:17) states that in Komo (Bantu D, D.R. Congo), 28 lexical tonal minimal pairs were found in a list of over 3,000 words, which is 2%. But even these quantifications are not as meaningful as they might be because they are based on word lists rather than natural texts, and because the authors give no detailed indication of how the counting was done. Comparison between Anyi Sanvi and Komo would only be possible if all the researchers had adopted a standardized procedure.

Functional load and the quantification of written ambiguities

We should also enumerate four ways in which our own research is distinct from most of the research on functional load. Firstly, those working on functional load are mainly concerned with oral language. Orthography developers, on the other hand, are primarily interested in written language, which in turn affects the research methodology and expected outcomes. Secondly, computational linguists tend to work on majority languages, and are therefore able to access massive, pre-existing, computerized corpuses. Those working on orthography development for minority languages such as Elip, Mbelime, and Eastern Dan, on the other hand, do not have this luxury because it can take several generations to generate a substantial body of literature. Thirdly, computational linguists tend to be concerned with evaluating the functional load of individual phonemic contrasts. That is not our concern here: The present study focuses on word-level lexical and grammatical ambiguities (cf. [START_REF] Unseth | Analyzing ambiguity in orthographies[END_REF][START_REF] Roberts | Exploring written ambiguities can help assess where to mark tone[END_REF]2015). This method, and experimental variations of it, has been applied successfully in numerous participatory orthography workshops across Africa (Kutsch Lojenga 1996). Fourthly, computational linguists use complex mathematical formulas that, for all their rigor and insightfulness, are far beyond the ken of most field linguists working on orthography development. Rather, what this latter group needs is a simple, standardized instrument for quantifying written tonal ambiguities if tone is not marked orthographically that they can employ when carrying out fieldwork.

Methodology

With these concerns in mind, we adopted the following methodology for our study. Our first concern was to move beyond mere word lists and investigate written ambiguities in natural texts. We translated the four narrative texts used by Bird (1999b:111-114) into Elip, Mbelime, and Eastern Dan, employing an oral translation method to ensure naturalness that we have described in detail elsewhere Language Documentation & Conservation Vol. 14, 2020 (Roberts submitted).⁵ Each text was transcribed with and without tone marks and interlinearized.

Because of the oral translation method used, texts differ considerably in length between languages. Table 1 reports the corpus sizes in terms of number of tokens (i.e., the number of orthographic words -defined as any letter or sequence of letters flanked by spaces), and the number of types (i.e., the number of distinct orthographic word forms) for both versions of the texts. The column headed "Difference" reports the number of orthographic words that participate in tonal minimal pairs in which both members of the pair occur in the corpus, giving a first indication of the level of written ambiguity in the three orthographies if tone is not marked. Then, in each language, we drew up a list of tonal minimal pairs in the versions of the four texts that were written without tone marks.⁶ For this purpose, we exploited all available resources. Three of the authors have extensive knowledge of one language each (Ginger Boyd for Elip; Johannes Merz for Mbelime; Valentin Vydrin for Eastern Dan). Published dictionaries were accessed in Mbelime (Sambiéni et al. 2004(Sambiéni et al. -2019) ) and Eastern Dan (Vydrin & Kességbeu 2008), as well as a yet unpublished lexical database and grammar sketch in Elip.⁷ But the most important resource to ensure the success of the methodology is the L1 informants' own knowledge of the language. Here the challenge is that even highly trained, literate informants are unlikely to be able to detect many written ambiguities as long as words are embedded in their natural contexts. In Mbelime we experimented with a technique to avoid this problem. Each word of the text was reproduced without tone marks on a separate card. The cards were then shuffled and presented individually to two informants in turn who wrote the various meanings of the word on the card and checked each other's work. The content of each card was then discussed with the researcher and further changes and additions made where necessary.

Once the data had been elicited in the three languages, we then separated them into lexical ambiguities (e.g., walk vs. sleep), grammatical ambiguities (e.g., he walked ⁵In fact the texts had to be translated from English into French first, as French is the official language of Cameroon, Benin, and Côte d'Ivoire. The texts were labeled SQUIRREL, EXILE, SORCERY, and PANTHER.

⁶A reviewer expressed the concern that it must be harder to identify tonal minimal pairs on the zero tone version of a text than on the full tone version. We disagree. Presented with a tone marked word, the informant would have to imagine what it might mean if it carried other tone marks. Presented with a zero tone-marked word, on the other hand, he or she only has to imagine what tone marks it could carry in order to convey meaning.

⁷An Elip lexicon of 1,625 words has been published on Webonary: https://elip.webonary.org/.

Language Documentation & Conservation Vol. 14, 2020 vs. he is walking), and cases where the two coincide (e.g., he walked vs. he is sleeping). We discarded repeated words and polysemy. Homophones were listed as primary and secondary meanings of a single form. We also discarded pairs that could not occupy the same syntactic slot. This meant that, for example, noun/verb pairs were not reported and that the infinitive was excluded from comparison with other conjugations because it never occupies the position of the main verb. However, this stipulation was set aside in individual cases, where it could be shown that syntactic context does not adequately disambiguate, as will be the case with one set of ambiguities in Eastern Dan (see §6.3.4).

In the phonemic and phonetic transcriptions that follow, the palatal approximant /j/ is transcribed /y/ following the Africanist tradition; nasal vowels are marked with a subscript tilde /◌̰ /; tone is marked with superscript diacritics: extra-high (xH) with a double acute accent /◌ ̋/, high (H) with an acute accent /◌ ́/, mid (M) with a macron /◌̄/, low (L) with a grave accent /◌ ̀/, extra-low (xL) with a double grave accent /◌ ̏/; and contour tones on single tone bearing units with combinations of these (specifically, LH /◌ ̌/ in Elip, MH /◌᷄ / in Mbelime, H-xL /◌ ̂/,⁸ and M-xL /◌̄/ in Eastern Dan).

We now turn to a presentation of the results in Elip⁹ ( §4), Mbelime ( §5), and Eastern Dan ( §6). In all cases, the form and meaning that actually occurs in the text is highlighted in bold.

Elip

4.1 Language overview Elip (ISO 639-3: ekm) is a Bantu A62 language (Grollemund 2012) spoken by about 20,000 speakers in the Mbam-et-Inoubou District of the Centre Region of Cameroon. The standard orthography has only recently been developed [START_REF] Boyd | Précis d'orthographe de langue nulibie[END_REF](Boyd /2015)).

Elip has twenty consonant phonemes: /b, d, g, t, k, ᵐb, ⁿd, ᵑg, f, s, h, f, ⁿtʃ, m, n, ɲ, ŋ, l, y, w/ (Boyd 2015a:117). In addition to prenasalized plosives, homorganic nasal noun class prefixes are attested (124).1⁰ The palatal nasal /ɲ/ is written <ni> in word initial position and as <ny> elsewhere. The velar nasal /ŋ/ is written <ŋ> and the prenasalised velar stop /ᵑg/ as <ng>.

Elip has eight vocalic phonemes /i, ɪ, e, a, u, ʊ, o, ɔ/ (Boyd 2015a:119), but they are represented by only seven graphemes in the orthography <i, ɛ, e, a, u, o, ɔ>. The phoneme /ɪ/ is represented as <i> in open syllables and as <ɛ> in closed syllables and word-finally. The same patterning is true of the corresponding back vowels. These spellings are all allophonic, corresponding to the pronunciation. Conversely, since the phoneme /i/ is spelled as <i> in all positions, the phonemes /i/ and /ɪ/ are under-⁸The circumflex usually indicates HL in African languages, but since this pattern is unattested on single vowels in Eastern Dan, it is available for signaling H-xL.

⁹The same kind of analysis of written tonal ambiguities was carried out on the closely related languages of Mmala and Yangben with similar results to Elip. represented in open syllables, and same is true of the phoneme /ɔ/ with respect to /ʊ/. Figure 1 summarizes these phonographic relationships. Elip has two contrastive tones, H and L, automatic and non-automatic downstep, and various morphotonological processes -that is, contextual tonal changes that occur across morpheme boundaries (Boyd 2015a:134-135). Certain lexical processes such as H tone spread are represented in the orthography, but non-automatic downstep is not. This is because L1 speakers are completely unaware of the phenomenon -they consistently hear ↓ H as H -and decision makers strongly resisted representing it. Post-lexical processes such as utterance-final H tone lowering and final-vowel devoicing/elision are not represented.

The orthography marks tone fully11 by means of diacritics (an acute accent to signal H tone <◌ ́> and absence of an accent to signal L tone <◌>). Since vowel length is not contrastive, contour tones on single tone bearing units are written by doubling the vowel, e.g. /a/ <aá>. Long vowels are (perhaps unfortunately) also written when necessary to respect the morpheme count within the conjugated verb.

Lexical tone

The Elip corpus contains only one lexical tonal minimal pair, both nouns, and both meanings occur, though not in the same text (1).

(1) a.

b.

/n y oɲı/ /n y oɲı/ <nionyi> <niónyi> market cry (n.)

11Or rather, "almost fully" because certain past tenses have a predictable floating H tone that docks onto the last TBU of the word; the decision was made to leave this tone under-represented (see example 7).

Language Documentation & Conservation Vol. 14, 2020

Grammatical tone

The Elip texts contain 43 words, all of them verbs,12 that participate in grammatical tonal minimal pairs, some of which are repeated. Of these, by far the most common contrast is between the narrative past and the present, of which there are 33 examples. In all cases, the correct (bold) interpretation in the texts is the narrative past ( 2)-( 6).

(2) a. b.

/abaň/

(s)he broke (s)he is breaking

The Elip texts contain eight words that participate in tonal minimal pairs between the recent and distant past. The meanings in the texts vary between the two tenses ( 7)-( 12).

( Mbelime has 14 consonant phonemes: /p, t, c, k, k ͡ p, b, ɖ, f, s, m, n, y, w, h/ (Neukom 2004:5). The labio-velar stop is written <kp> and the retroflex plosive /ɖ/ as <d>. It also has seven contrastive vowel phonemes /i, e, ɛ, a, u, o, ɔ/, all of which may be nasalized (Neukom 2004:7).

Mbelime has three contrastive level tones, H, M and L, contour tones, downstep, upstep, and various morphotonological processes (Liu 2013; Melick 2012). Lexical processes such as L tone spread are represented in the orthography, while postlexical ones such as upstep of successive H tones are not. In terms of orthographic depth, then, the orthography represents the output of the lexical phonology, as recommended by [START_REF] Snider | Orthography and phonological depth[END_REF][START_REF] Snider | Tone analysis for field linguists[END_REF]. The orthography, at the time this research was 13This may be a case of a recent past verb which is best rendered in English as present continuous.

Language Documentation & Conservation Vol. 14, 2020 conducted, marked H tone with an acute accent /◌ ́/, M tone with a macron /◌̄/, and L tone with absence of an accent /◌/.1⁴ Contour tones are under-represented. The last example in this set deserves special attention because when the two words appear without class prefixes their meanings are in and on respectively, and the four meanings together have a highly unbalanced distribution in the corpus: <hı̰ ̄nnı̄> 'in' (12 times), <ı̄hı̰ nnı̄> 'inside' (4), <hı̰ ń́n ı > 'on' (1), <ı̄hḭ́ ńní> 'sky' (0). We will return to the question of how to assess such imbalances in a discussion on methodology refinement ( §8.1). 1⁴The data in this article is transcribed using the orthography that was in use when the research was conducted. Since then, there has been a spelling reform. See §8.3 for further details.

5.2

Verbs

1⁵In the course of this analysis, we found five words in the Mbelime texts in which class prefixes had been written joined to the noun root. Since this was incorrect spelling at the time of the experiment (it is another aspect of the 2017 reform), we excluded these from the list of tonal minimal pairs.

1⁶In Mbelime, the neutral aspect is used to express both the imperative and the future. The Mbelime texts contain one verb that participates in a grammatical tonal minimal triplet between the neutral, the imperfective and the habitual (20). Two of the three meanings occur in the texts.

(20) a. b. c. 1⁷This meaning occurs twice in consecutive sentences in the SORCERY text. In the first occurrence, it is spelled incorrectly as <póó>.

/pēdìmù

1⁸Our Mbelime informant considers <huusí> [hùùsí] to also be an acceptable spelling and pronunciation for this meaning.

Language Documentation & Conservation Vol. 14, 2020

The Mbelime texts contain eleven words that participate in tonal minimal triplets in which lexical and grammatical tone coincide ( 23)-( 24).

( Eastern Dan has twelve oral vowels /i, e, ɛ, ae, ɯ, ɤ, ʌ, a, u, o, ɔ, ɒ/. In the 1982 orthography, the phonemes /ɯ, ʌ, ae, ɒ/ are written <ü, ë, ɛa, aɔ> respectively. The phonemes /e, o, ɤ/ are pronounced [ɪ, ʊ, ұ2⁰] and written <ɩ, ʋ, ʋ> on a xH tone syllable, and [e, o, ɤ] <e, o, ö> elsewhere, respectively.21 There are nine nasal vowels /ḭ , ɛ̰ , ae ̰ , ɯ ̰ , ʌ̰ , a̰ , ṵ , ɔ̰ , ɒ̰ / spelled <in, ɛn, ɛan, ün, ën, an, un, ɔn, aɔn>. All of the vowels -oral and nasal -can appear in a sequence of two identical vowels. In addition, the velar nasal /ŋ/ is also best interpreted as a vowel, because it occurs in the same phonotactic slot as vowels and bears tone as vowels do (SIL 1982:8;Vydrin & Kességbeu 2008:7-9).

The 21This allophony is contrastive in some dialects.

Language Documentation & Conservation Vol. 14, 2020 punctuation strategy cannot mark tone word-medially.22 Eastern Dan has practically no morphotonological processes (SIL 1982:12-13;[START_REF] Bolli | The teaching of tone in the Dan language[END_REF]Vydrin & Kességbeu 2008:10-11).

6.2 Lexical tone 6.2.1 Nouns The Eastern Dan texts contain twelve nouns that participate in lexical tonal minimal pairs (25); four nouns that participate in lexical tonal minimal triplets (26); one noun that participates in a lexical tonal minimal quadruplet (27); and one noun that participates in a lexical tonal minimal quintuplet (28). In the latter case, two of the five meanings occur in the texts. Notice that this set -and all of the following ones -also contains numerous homophones indicated in the glosses by numbering. Thus, even though tone is written fully, the degree of written ambiguity remains relatively high.23 ( 25 ). On words of two or more feet, the final tone is not marked, even though in principle it could be (e.g., /fáŋkpɛɛ/ <'fangkpɛɛ> 'Black-and-white tailed hornbill').

23We also counted tonal minimal pairs in the current version of the dictionary database, which by now contains about 25% more entries than the published version (Vydrin & Kességbeu 2008). Among the 1,858 lexical noun forms -the vast majority of which are monosyllabic -we found 143 pairs, 41 triplets, 8 quadruplets, and 2 quintuplets. This count does not include numerous cross-category pairs for the reasons stated in §3.

2⁴"Panther" is the principal character in the PANTHER text, but it is the more common synonym /gweē/ <gwee> that is used. In all of the examples in this list, the infinitive also contrasts with the neutral and conjoint, making tonal minimal triplets, and additional contrasts including the infinitive would expand the list to ten. However, the infinitive was excluded from the analysis on the grounds that it does not occupy the same syntactic slot as the other conjugations in the triplet. A further 18 words that participate in tonal minimal pairs between the infinitive and the neutral were excluded for the same reason.

Language

The Eastern Dan texts contain many verbs in which lexical and grammatical tone coincide. Four words participate in tonal minimal pairs (34); two words participate in tonal minimal triplets (35); and one word participates in a tonal minimal quintuplet (36). In two cases (34)-( 35), both lexical meanings occur in the texts. Again, if the infinitive were included in the analysis, this list would expand considerably.

(34) a.

b.

/pɤ̄

hear (LEX, CJT) 2. cook (LEX) appear (LEX) beat (LEX, INF) appear (INF) hear (INF) 2. cook (INF)

2⁷In Eastern Dan, the neutral aspect is a default construction expressing numerous TAM meanings (habitual, stative perfect, progressive, imperfect, resultative, and completive).

Language Documentation & Conservation Vol. 14, 2020 6.3.3 Predicative markers Verb conjugations are also distinguished by the forms of the pronominal predicative markers, of which each has its own series and many of which are distinguished uniquely by tone. The Eastern Dan texts contain seven predicative markers that participate in grammatical tonal minimal pairs (37)-( 38) and eight that participate in grammatical tonal minimal triplets ( 39)-( 40).

(37) a.

b. 41)-( 46) contain items that belong to different parts of speech, yet they can still occupy positions where they can easily be misinterpreted, especially by non-fluent readers. For example, the eight nominal meanings of the word <gban> (47) would fit neatly into the analysis above, except that, as it happens, none of them appear in the texts. The meaning that does occur is the determiner 'all, entire' which automatically excludes the entire set from the analysis on the grounds that nouns and determiners do not share the same syntactic slot.

/ɓa ́á

( But this procedure for systematising the data overlooks the fact that the word <gban> may well be mistaken for a noun or a determiner when the two occupy the same position in a sentence, for example in (48).

Language Documentation & Conservation Vol. 14, 2020

a. /ȁ gbā tɔ̏gba̰ ̋ká/ <-a gba -tɔ ˈˈgban ˈka> give him a chicken leg 3SG.NSBJ give chicken leg with b. /ȁ gbā tɔ̏gbā̰ ká/ <-a gba -tɔ gban ˈka> give him a chicken wing 3SG.NSBJ give chicken wing with c. /ȁ gbā tɔ̏gbà̰ ká/ <-a gba -tɔ =gban ˈka> give him all the chickens2⁸ 3SG.NSBJ give chicken all with Similar ambiguities are possible in the following five tonal minimal pairs and triplets ( 49)-( 53). ( 49 7. Quantifying the ambiguities We are now in a position to attempt a simple quantification of tonal ambiguities if tone were not marked orthographically in the three languages. In Tables 2-5 below, for each language, the left-hand column reports the raw number of ambiguous words detected. Then in the right hand column, to account for all possible contrasts (Schroeder 2008:56;[START_REF] Chen | Homophone density and phonological frequency in Chinese word recognition[END_REF]Huff & Payne 2012), tonal minimal triplets are multiplied by three (because there are three possible pairs: AB, AC, BC); quadruplets by six (AB, AC, AD, BC, BD, CD); quintuplets 2⁸The plural marker <-nu> [ɓṵ ] is absent when a noun is followed by the determiner <=gban> [gbà̰ ] 'all, entire'.

Language Documentation & Conservation Vol. 14, 2020 by ten (AB, AC, AD, AE, BC, BD, BE, CD, CE, DE); and, in one case, a sextuplet by fifteen (AB, AC, AD, AE, AF, BC, BD, BE, BF, CD, CE, CF, DE, DF, EF). The raw totals are the sums of the sub-totals. The latter is then divided by the corpus size -which varies considerably between languages because of the oral translation method usedto attain a percentage. Table 2 presents a summary of the lexical tonal ambiguities if tone is not marked orthographically in the three languages. These are verging on non-existent in the Elip texts, whereas Mbelime has many, especially among verbs. As for Eastern Dan, although the overall score is higher than the other two languages, pure lexical tone is concentrated in the nouns, and completely absent among verbs. Table 3 summarizes the grammatical tonal ambiguities if tone is not marked orthographically. All three languages attest grammatical tone among verbs, but this is not where the tonal ambiguities in Mbelime come to the fore, in spite of having triplets as well as pairs. Elip and Eastern Dan have similar scores on grammatical tone. In spite of Elip having no groupings larger than pairs, it has a few verb conjugations that are frequent in narrative texts. Eastern Dan, on the other hand, is the only language to have (limited) grammatical tone on nouns, and in which categories other than nouns and verbs are needed when cataloguing grammatical tone, including predicative markers, other parts of speech, and a separate statement covering pairs that are ambiguous in spite of not sharing the same syntactic slot. This latter category contains the only sextuplet in the whole analysis. Table 4 summarizes the ambiguities in which lexical and grammatical ambiguities coincide. Elip scores zero in this category because it has no lexical pairs among verbs. Mbelime, on the other hand, has a good deal of interplay between lexical and grammatical tone scoring higher than Eastern Dan on this measure, in spite of the latter language boasting one quintuplet. Table 5 summarizes the level of written ambiguity in the three languages if tone is not marked in the orthographies, combining scores for lexical tone, grammatical tone, and cases where lexical and grammatical tone coincide. Elip and Mbelime have similar scores, but both are eclipsed by Eastern Dan. ) are tonal minimal pairs, so it is likely that an analysis of a larger text corpus might reveal results quite different from those presented above. Roberts (2010:29), for example, needed a corpus of over 142,000 words and containing a wide range of text genres to capture the most infrequent cases of grammatical tone in Kabiye. Should all ambiguities be given equal weight? Our analysis overlooks the strong likelihood that grammatical ambiguities, by their very nature, are often more easily confusable in context than lexical ones. It may also be desirable to assign greater weight to tonal ambiguities in which both words occur in the text than to those in which only one of the pair occurs. Then, in the former case, pairs that appear in the same visual field are surely more ambiguous than those that are distant from each other. Faced with data such as the last item in Mbelime example (15), with its highly unbalanced distribution of meanings, it may also be wise to take into account Kadyamusuma & Kadenge's (2013:88) distinction between balanced homographs, (i.e., those with two equally frequent meanings) and biased homographs (i.e., those with one meaning that is more frequent).

Furthermore, while our analysis takes syntactic context into account, it ignores the much greater challenge of quantifying the contribution of semantic context. In Elip, the simple past is often the obvious semantic choice once the reader has recognized the narrative nature of the texts, e.g., examples (2)-( 6). In Mbelime, the lexical pair 'bag' vs. 'trunk' (15d) is much more semantically confusable than 'dog' vs. 'weak heart' (15b).

A reviewer has questioned whether the study paid enough attention to morphotonological processes, given that, depending on how they are written, they may blur the distinction between lexical and grammatical tone. We investigated this point with respect to lexical L tone spread in Mbelime but found no evidence that it leads to ambiguity. This is because the full tone version of the orthography represents the output of the Lexical Phonology -correctly, we believe -and leaves surface postlexical processes unrepresented.

As another reviewer has noted, high-frequency ambiguities such as pronominal tonal minimal pairs may impact reading fluency at several points in one text, so perhaps it is not advisable to discard repeated words. This is a valid point, although it would be necessary to control for the fact that oral reading errors of any difficult words, not just tonal minimal pairs, tend to decline with repeated occurrences within a single text, as demonstrated in Eastern Dan (Roberts & Vydrin 2019) and Kabiye (Roberts 2008:360-361).

Yet another concern is whether it is acceptable to compare written ambiguities between languages that have differing levels of resources to help identify them. One informant may be particularly adept at spotting potential ambiguities, while another needs more training and supervision. One researcher may have an extensive knowledge of the language structure, making it possible to suggest hypothetical ambiguities to an informant, while another has little or no such knowledge. One language may be well documented, while another is under-documented. At the very least, such variables need to be admitted when the proposed methodology is applied crosslinguistically. Doubtless all of these issues leave room for improvement. However, we have a lingering concern that, if future researchers end up cherry picking from the discus-Language Documentation & Conservation Vol. 14, 2020 sion points above, the domain will continue to be hampered by non-standardized methodologies, and paradoxically this article will have failed in its primary purpose.

Additional experimental data

The data presented in this paper emerge from a wider research project testing reading and writing fluency in ten Niger-Congo languages. In an experiment design modeled on Bird (1999b), 308 participants orally read unmarked and marked versions of the same four translated narrative texts.

Tellingly, the experiment results show no statistically significant evidence of the need to mark tone fully in Elip, and only patchy evidence in Mbelime and Eastern Dan. The presence or absence of full tone marking does not contribute to oral reading speed in any of these three languages, neither does it enhance accuracy in Elip. It may, cautiously, increase tonal accuracy in Mbelime (by 43.46%, p = 0.090) and general accuracy in Eastern Dan (by 18.95%, p = 0.094), and it definitely improves comprehension in Mbelime (by 13.90%, p = 0.036). As for the supplementary task of adding tone marks to unmarked texts, scores are pitifully low in Elip (30.15% mean success rate), and far from spectacular in Mbelime (68.69%) and Eastern Dan (61.11%). For a fuller report, see Roberts (submitted).

Spelling reform

Orthography stakeholders in all three languages have also been involved in a lengthy process of spelling reform spanning the period of the research project. In Elip, they have recently veered towards a surface-tone marking system at the cost of consistent word images, apparently motivated by a concern for the needs of non-L1 speakers.2⁹ In Mbelime, decision makers recently aligned themselves with Beninese government recommendations (CENALA 2011) by reversing two of the tone marks. From now on, L tone will be marked with a grave accent and M tone will be unmarked (CNLM 2017:9;Merz et al. 2017:11; see Appendix, Figure 6). As for Eastern Dan, decision makers have recently adopted a radical spelling reform that employs superscript diacritics for marking tone, biunique segmental correspondence, and special characters for marking vowels (Roberts et al. 2019;[START_REF] Vydrin | Guide de nouvelle orthographe dan de l'est pour les apprenants familiers avec l'ancienne orthographe[END_REF]; see Appendix, Figure 9). In all three languages, then, full tone marking has survived recent spelling reforms. None of them, at this stage in their development, is investigating other possibilities such as the partial marking of grammatical tone (Kutsch Lojenga 1993), or zero marking for fluent readers, following the precedent of Hebrew vowel pointing [START_REF] Frost | Reading consonants and guessing vowels: Visual word recognition in Hebrew orthography[END_REF].

Conclusion

In closing, let us return to the proposed methodology for quantifying tonal ambiguities. We firmly align ourselves with the view that it would be undesirable to set up a mechanical, numerical threshold above which tone must be marked fully in an orthography (Gordon 1986:76;Unseth & Unseth 1991:46). Nevertheless, we offer this methodology as a tool for orthography developers seeking a standardized, simple procedure for measuring written ambiguities if tone is not marked in a tone language. It will also provide a promising basis for any researcher wishing to develop a quantitative typology of tone systems based on the functional load of tone in the lexicon and the grammar. For whatever purpose it is employed, we hope to have also shown that there is nothing dishonorable about evaluating the functional load of tone -recalling King's definition with which we began this article -"in its simplest expression".

Abbreviations

Elip

Figure 2. ELIP written with full tone marking (2015 orthography)

Na Ombo ́ge na Mbua ́bamɛɛ d ga ́gue ben ikumb. Bamaa baa ńda ́Ombo ́ge uganyɛ ga ́Mbua ́ań ee : ‹‹Yaŋua ́ŋŋaa bulı ǵanɔ ugua ́bukumb ga ́giagia ́yaŋua ́nnyɛ mɔnɔ ńuɔ ĺ.» -Yö-këyi do 'ka -gbeng waa-'gbɛn--wo -kë"taɔngdëdhɛ 'gü, 'wo =niëëwo 'ko "piʋ̈. 'Yö--nu -wo -yö-këdo kö-wo "kpaɔ 'sükö-wo 'dho see" =kwaan-.

  1⁰The phoneme /ⁿs/ and the sequence /n̩ s/ are pronounced [ⁿtʃ] and [n̩ tʃ] respectively in the Yambassa reference dialect, and as [ⁿs] and [n̩ s] respectively in the Balamba and Mana-Kanya dialects. They are both spelled invariably as <ns>. Language Documentation & Conservation Vol. 14, 2020

Figure 1 .

 1 Figure 1. Over-and under-representation of vowels in Elip

  1982 orthography uses punctuation symbols placed word-initially and wordfinally to signal tone. It has five phonemic level tones(xH /◌ ̋/ <ˈˈ◌>, H /◌ ́/ <'◌>, M /◌̄/ <◌>, L /◌ ̀/ <=◌>, xL /◌ ̏/ <-◌>), four falling contours (xH-xL /◌ ̋◌ ̏/ <ˈˈ◌◌->, H-xL /◌ ́◌ ̏/ <'◌◌->, M-xL /◌̄◌ ̏/ <◌◌->, L-xL /◌ ̀◌ ̏/ <=◌◌->),and two rising contours (M-H /◌̄◌ ́/ <◌◌'>, H-xH /◌̄◌ ̋/ <◌◌ˈˈ>). Occasionally contour tones occur on single short vowels. There is a limited amount of under-representation of longer words, since the 1⁹The data in this article is transcribed following the 1982 orthography, but recently there has been a spelling reform. See §8.3 for further details.

2⁰Following

  Vydrin & Kességbeu (2008:7), we use this symbol to indicate a near-close near-back unrounded vowel.

2⁹We

  have not reproduced the reformed Elip orthography in the Appendix because we are unsure of the exact nature of the changes. Language Documentation & Conservation Vol. 14, 2020

Figure 3 .MbelimeFigure 4 .Figure 5 .

 345 Figure 3. ELIP written with zero tone marking

Figure 6 .Figure 7 .

 67 Figure 6. MBELIME written with full tone marking (2017 orthography)

Figure 8 .

 8 Figure 8. EASTERN DAN written with zero tone marking (1982 orthography)

Figure 9 .

 9 Figure 9. EASTERN DAN written with full tone marking (2019 orthography)

Table 1 . Corpus sizes Tokens Types Zero tone texts Full tone texts Difference

 1

	ELIP	427	223	233	10
	MBELIME	956	230	254	24
	EASTERN DAN	743	158	219	61

<tóńtá> <cɔ̄ɔ̄tɔ> <kuutá> <yōotā> arrive (NEU) take girl as wife (PRF) go back into (IPF) raise hand (NEU)

  The Mbelime texts contain eight verbs that participate in lexical tonal minimal pairs (16).

	(16) a.	/tóńtá/		/tōn̄tá/	<tōn̄tá>	unbutton (NEU)
	b.	/cɔ̄ɔ̄tɔ /		/cɔ ɔt ɔ /	<cɔ ɔt ɔ>	calcify (PRF)
	c.	/kuutá/		/kūùtā/	<kūutā>	pound badly (IPF)
	d.	/yōòtā/		/yōōtá/	<yōōtá>	speak (NEU)
	The Mbelime texts contain six verbs that participate in lexical tonal minimal triplets
	(17)-(18).
	(17) a. /būūní/ <būūní> judge (NEU) 1⁶
	b.	/būùnı̄/	<būunı̄>	grind badly (NEU)
	c.	/búúní/	<búúní>	brew (NEU)

  Lexical and grammatical tone The Mbelime texts contain five words that participate in tonal minimal pairs in which lexical and grammatical tone coincide (21)-(22).

			/	<pēdimu>	explain (NEU)
		/pédímú/	<pédímú>	explain (HAB)
		/pèdìmú/	<pedimú>	explain (IPF)
	5.4 (21) a.	/bàsí/	<basí>	choose (IPF)
	b.	/bāsı̄/	<bāsi>	meet (NEU)
	(22) a. b.	/tɛ̄/ /tɛ / <tɛ̄> <tɛ>	belong to (PRF) be nasty (PRF, HAB, NEU)

  Language overview Eastern Dan (ISO 639-3 dnj) is a South Mande language spoken by about 650,000 people in and around the town of Man in the Montagnes district of Côte d'Ivoire (Eberhard et al. 2019). The orthography that was being used at the time of our research was standardised in 1982.1⁹ Eastern Dan has 17 consonant phonemes /p, t, k, kp, b, d, g, gb, f, s, v, z, ɓ, ɗ, l, y, w/ (SIL 1982:4; Vydrin & Kességbeu 2008:9-10). In the 1982 orthography, the phonemes /ɓ, ɗ/ are pronounced and spelled [m, n] <m, n> preceding a nasal vowel and [ɓ, ɗ] <bh, dh> elsewhere, respectively. The phoneme /l/ is pronounced [ɾ] and spelled <r> following a coronal consonant, and [l] elsewhere.

	) a.	/hı̄ı̄/	<hı̄ı̄>	die (NEU)
	b.	/híì/	<híi>	die (PRF)
	c.	/hı̄ı̄/	<hı̄ı̄>	stare (NEU, PRF, IPF)
	(24) a.	/hōǹsı̄/	<hōnsı̄>	fight (IPF, NEU)
	b.	/hōn̄sí/	<hōn̄sí>	dry quickly (NEU, IPF)
	c.	/hóńsí/	<hóńsí>	be greedy (PRF)
	6. Eastern Dan
	6.1

  Verbs Eastern Dan has three tonally inflected conjugated forms (infinitive, neutral and conjoint) plus the lexical form. The lexical, neutral, and conjoint forms share the same syntactic slot. The Eastern Dan texts contain six verbs that participate in grammatical tonal minimal triplets in which the lexical, neutral,2⁷ and conjoint aspects contrast (33). In two cases, all three conjugations appear in the text.

	(28) a. b. c. d. e. 6.3.2 (33)	/kwɛ̋ɛ̋/ /kwɛ̄ɛ̄/ /kwɛ̏ɛ̏/ /kwɛ̄ɛ̋/ /kwɛ ɛ̏/	<ˈˈkwɛɛ> <kwɛɛ> <-kwɛɛ> <kwɛɛˈˈ> <=kwɛɛ->	door part of a loom old man hand load
	6.2.2 Verbs The Eastern Dan texts contain no verbal tonal minimal pairs that are LEXICAL NEUTRAL CONJOINT
	purely lexical. All tonally ambiguous verbs contain complex interactions between a. /ɗó/ <ˈdho> /ɗȍ/ <-dho> /ɗō/ <dho> go
	lexical and grammatical tone (see §6.3.2).2⁵ b. /gó/ <ˈgo> /gȍ/ <-go>	/gō/ <go>	1. go away 2. sell
	c. /kṵ̋/		<ˈkun> /kṵ̏/	<-kun> /kṵ̄/ <kun>	catch
	d. /ɓɔ̰ ̄ɔ̰ ̏/ <mɔɔ-> /ɓɔ̰ ̏ɔ̰ ̏/ <-mɔɔ> /ɓɔ̰ ɔ̰ / <=mɔɔ> search 6.3 Grammatical tone e. /sɯ ́/ <ˈsü> /sɯ ̏/ <-sü> /sɯ ̄/ <sü> take
	f. /tó/		<ˈto>		/tȍ/	<-to>	/tō/	<to>	remain
	6.3.1 Nouns (case markers and pronouns) The Eastern Dan texts contain two nouns
	that participate in grammatical tonal minimal pairs (29) and triplets (30) where the
	isolation form contrasts with the head marked and/or the relativized form. In exam-
	ple (30), all three meanings occur in the texts.
	(29) a.	/gbő/	<ˈˈgbo>	crying
	b.	/gbȍ/	<-gbo>	crying (+ head marker)
	The Eastern Dan texts contain a noun (31) and a reciprocal pronoun (32) that partic-
	ipate in grammatical tonal minimal pairs where the superessive case form contrasts
	with the isolation form or the comitative case form.
	(31) a.	/kwɛ̄ɛ̋/	<kwɛɛˈˈ>	hand
	b.	/kwɛ ɛ̏/	<=kwɛɛ->	hand (superessive case)
	(32) a.	/kwʌ̋ʌ̋/	<ˈˈkwëë>	each other (comitative case)
	b.	/kwʌ ́ʌ̏/	<ˈkwëë->	each other (superessive case)
	2⁵Among the 319 lexical verb forms in the current version of the dictionary database, we found 20 pairs and
	1 triplet. The current database includes forms with preverbs (separable quasi-prefixes), such as /ɗıɤ-pa/
	<ˈˈdhiö pa> 'to complete' and /ta-kpa/ <-ta kpa> 'to stick up', which are systematically written disjunctively
	in the 1982 orthography.
	2⁶This form is usually written conjunctively with the preceding word, and thus, according to the 1982
	spelling rules, its tone is unmarked.
						Documentation & Conservation Vol. 14, 2020 Language Documentation & Conservation Vol. 14, 2020

(30) a. /ɓɛ̰ ̄/ l<mɛ> llhuman b. /ɓɛ̰ / l<-mɛ> lhuman (+ head marker)2⁶ c. /ɓɛ ̰́ / <ˈmɛ> human (+ relativization marker)

search (LEX) 1. be able, reach (LEX, CJT) 2

			/	<pö>	say (LEX, CJT)
		/pɤ̏/	<-pö>	fall (LEX, NEU, CJT)
	(35) a.	/ɓɔ̰ ̄ɔ̰ ̏/	<mɔɔ->
	b.	/ɓɔ ̰̀ ɔ ̰̀ /	<=mɔɔ>	. search (CJT)
	c.	/ɓɔ̰ ̏ɔ̰ /	<-mɔɔ>	1. be able, reach (NEU) 2. search (NEU)
	(36) a.	/ɓa̰ /	<ma>
	b.	/ɓa ̰́ /	<ˈma>
	c.	/ɓa̰ /	<-ma>
	d.	/ɓa̰	̂/	<ˈma->
	e.	/ɓa̰ ̄/	<ma->

  Outstanding pairs Finally, we need to admit that many ambiguities in the Eastern Dan texts defy easy categorization because the functional load of tone is so extraordinarily heavy. All of the pairs and triplets in examples (

	(44) a.	/sı̄ʌ̄/	<sië->	durative marker
		b.	/sı ʌ̀/	<=sië>	sometimes; often
	(45) a.	/yɤ ́/	<ˈyö>	consecutive conjunction
		b.	/yɤ̂/	<ˈyö->	consecutive conjunction + 3SG non-subject pronoun
				/	<ˈbhaa>	1. 2SG NEG IPF 2. certain + 3SG NEG PRF
	(46) a. b.	/ɓāȁ/ /zɯ ́/ /zɯ ̏/ <ˈzü> <bhaa-> any more, more 2SG presumptive <-zü> around
	(38) a.	/wȁȁ/	<-waa>	3PL PRF predicative marker + 3SG non-subject pronoun
	6.3.5	b.	/wa ́á/	<ˈwaa>	3PL NEG IPF predicative marker
	(39) a.	/wa ́á/	<ˈwaa>	3PL NEG IPF
		b.	/wȁȁ/	<-waa>	3PL subjunctive + 3SG non-subject pronoun
		c.	/wāȁ/	<waa>	3PL presumptive
	(40) a.	/ya ́á/	<ˈyaa>	1. 3SG NEG IPF 2. CNJ + 1SG CJT 3. 1PL EXC NEG IPF
		b.	/ya à̏/	<=yaa->	3SG PRF + 3SG non-subject pronoun
		c.	/yāȁ/	<yaa->	1. 3SG presumptive 2. 1PL EXC presumptive
	6.3.4 Other parts of speech This leaves a miscellany of six words from other parts
	of speech that participate in tonal minimal pairs (41)-(46). In two cases, two of the
	various meanings occur in the text.
	(41) a.	/ɓá/	<ˈbha>	certain, one
		b.	/ɓā/	<bha>	1. definite article 2. equative copula 3. there (near the listener)
	(42) a.	/kó/	<ˈko>	each other
		b.	/kō/	<ko>	1. 1PL.DUAL.INC autonomous pronoun
		l	l	l		2. 1PL.DUAL.INC non-subject pronoun
	(43) a.	/klɤ̄ɤ̏/	<klöö->	short
		b.	/klɤ̄ɤ̋/	<klööˈˈ>	short (intensive)
						Language Documentation & Conservation Vol. 14, 2020

Table 2 .

 2 Lexical tonal ambiguities in the Elip, Mbelime, and Eastern Dan texts

		ELIP		MBELIME	E. DAN
	Lexical tone (nouns)
	Pairs (x 1)	1	1 11	11 12	12
	Triplets (x 3)	0	0	0	0	4	12
	Quadruplets (x 6)	0	0	0	0	1	6
	Quintuplets (x 10)	0	0	0	0	1	10
	Sub-total		1		11		40
	Lexical tone (verbs)
	Pairs (x 1)	0	0	8	8	0	0
	Triplets (x 3)	0	0	6	18	0	0
	Sub-total		0		26		0
	Raw total		1		37		40
	Corpus size		427		956		743
	% Total	0.23%		3.87%	5.38%

Table 3 .

 3 Grammatical tonal ambiguities in the Elip, Mbelime, and Eastern Dan texts

Table 4 .

 4 Ambiguities in which lexical and grammatical tone coincide in the Elip, Mbelime, and Eastern Dan texts

	ELIP	MBELIME	E DAN

Table 5 .

 5 Summary of written ambiguities in Elip, Mbelime, and Eastern Dan if tone is not fully marked Refining the methodology The methodology proposed in this paper might benefit from further refinement in several respects. Our main concern is that the corpuses are not large or varied enough for an exhaustive analysis. The Mbelime corpus is inevitably more reliable than the Elip corpus merely by virtue of being over twice the size. Of the 471 verbs in the Elip lexical database, 22 (4.7%

		ELIP MBELIME	E DAN
	Lexical tone	0.23%	3.87%	5.38%
	Grammatical tone	10.07%	0.94% 11.17%
	Lexical and grammatical tone	0.00%	3.97%	2.69%
	TOTAL	10.30%	8.78% 19.24%
	8. Discussion
	8.1

  .Figures2-9show the first paragraph of the SQUIRREL text in the three languages with full tone marking, zero tone marking, and, where appropriate, the recent spelling reforms.

	CJT	conjoint
	CNJ	conjunction
	EXC exclusive
	H	high tone
	HAB habitual
	INC	inclusive
	INF	infinitive
	IPF	imperfective
	L	low tone
	LEX	lexical
	M	mid tone
	n.	noun
	NEU neutral
	NEG negative
	Nsbj non-subject series of personal pronouns
	PL	plural
	PRF	perfective
	SG	singular
	xH	extra-high tone
	xL	extra-low tone

LanguageDocumentation & Conservation Vol. 14, 2020

*The Eastern Dan part of this research was supported by a public grant overseen by the French National Research Agency (ANR) as part of the "Investissements d'Avenir" program (reference: ANR-10-LABX-0083).

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