In this paper, we show that building a treebank can be used as a way to establish a language. Annotated corpus can be used as tools when arguing that some linguistic data belongs to a separate language (rather than a dialect or variety of another established language). We provide here a case study on a treebank of Naija, a Post-creole spoken in Nigeria which presents us with significant differences from treebanks of English in terms of existing constructions and frequency of several syntactic units. Spoken by educated Nigerians, the Nigerian post-creole has been shown by Deuber (2005) to develop in Lagos as a discrete language, separate from Nigerian English. This language, that we propose to call Naija, is now spoken as a second language by over 100 million speakers, all over Nigeria, a country of 180 millions people, where about 450 native languages are spoken with three dominating languages (Igbo, Yoruba, and Hausa). This new language has taken a considerable economical and cultural importance in Nigeria. Nevertheless, for its speakers, this language is often considered as an inferior version of English (they call it “Broken”) with a negative influence on Nigerian education. Most speakers are not conscious that, as a separate language with its own grammar and lexicon, it has a outstanding potential in favor of national cohesion, since it is perceived as ethnically neutral, and for regional integration, due to its intercomprehension with Ghanaian and Cameroonian pidgins.
Considering the particular situation of this language, building a syntactic treebank takes a particular significance. Of course, as for any language, a treebank can be useful for many applications, such as the training of a syntactic parser. But here the treebank helps us to establish the existence of Naija as a language separate from (Nigerian) English, by showing constructions that are specific to Naija (qualitative analysis) and constructions that are over-represented in Naija (quantitative analysis). The study is based on a 750,000 word corpus collected all around Nigeria. The transcription is a scientific and political challenge by itself because most words stem from English, but some of them have grammaticalized and are pronounced differently. We follow what is done in the (mostly informal) writing of Naija: keep the English spelling for lexical words, with exceptions for very frequent words such as broda ‘brother’; and a more phonetic spelling for grammatical terms (dem ‘them’, im ‘him’, sey complementizer lit. say).
Naija also borrowed lexical items from other local
languages, in particular ideophones such as kpatakpata
‘completely’.
(1) sotay di rain sef kuku fall some house
dem down kpatakpata
so_that the rain EMPH commonly fall some house
PL down completely
‘So that, often, the rain completely destroys houses.’
We use the Arborator
In order to allow for typological comparison and distance
measures on Naija, we use a surface-syntactic dependency
annotation scheme that is compliant with standard
dependency annotation (e.g. prepositions as governors)
and thus easy to learn and to apply, but which allows for a
lossless transformation into Universal Dependencies (UD)
by means of a graph rewriting process
3.
A good number of morphosyntactic specificities of Naija
have called for an ongoing review of the annotating
scheme that was initially adopted for the language.
Some of these specificities are linked to the influence of
adstrate vernacular languages belonging mainly to the
Niger-Congo family. This is the case of emphatic
adverbial particles (e.g. sha, o) tagged with the ADV POS
label, but whose function is characterized by the
mod:emph dependency link. The influence of adstrate
vernacular languages is observed in the use of Serial Verb
Constructions, that is “monoclausal construction[s]
consisting of multiple independent verbs with no element
linking them and with no predicate-argument relation
between the verbs.”
The same ongoing grammaticalization process is observed in the formation of TAM auxiliaries where full lexical verbs (e.g. go ‘go’; come ‘come’ ; dey ‘exist’) coexist with their grammaticalized equivalents (go, future; come, realis; dey, imperfective). Likewise, the verb make, which already appears in Serial Verb Constructions to express the equivalent of the comitative case, is used as an auxiliary for converb forms (e.g. dem want make e go church ‘they want him to go to church’). This flourishing multifunctionality, typical of creole languages, creates challenges for the recognition of government.
In creoles, it is usually assumed that there is a division of labor between the lexifier language which provides the majority of the lexicon (in our case English) and substrate languages in areal contact with the creole (in the case of Naija these might be Yoruba, Igbo and Hausa for example). We attempt to show quantitative evidence of structural similarities and differences between Naija and English.
One of our hypothesis concerning these differences is that
information packaging (or communicative structure) plays
a larger role in Naija than in English. To explore this
hypothesis it is necessary that we dispose of an annotated
corpus, as we need to measure the frequency of some
structures (for example dislocations and cleft sentences),
rather than their strict presence or absence in the
language. For this purpose, we use all available treebanks
of English in UD v2.1: UD_English-ParTUT
(1) (2) (3)
Verb / Auxiliaries ratio 1.9 1.8 2.0
Taking into account the fact that Naija also has the highest frequency of auxiliaries (9.3% against 4.2% for written English and 4.6% for spoken English) we observe that Naija must compensate by having a high frequency of verbs which can be accounted for by the compound:svc, ccomp, acl:relcl and root relations. If we look more precisely at the distribution of these auxiliaries, it appears that it is the auxiliaries which are not shared with English (dey, come, go, don, fit, for and neva) which are more frequent, while there is only one occurrence of the shared auxiliary will. between written and spoken French, which seems to suggest that this might very well be a product of the genre rather than a characteristic of the language.2 The lower frequencies for both oblique and case relations are correlated: Naija seems to use less oblique complement in favor of more direct objects. Locative complements can be expressed through Serial Verb Constructions with the place as direct object of the second verb as in (3). (3) government worker dem go dey enter go work government worker PL FUT PROG get_on go work ‘government workers will be getting on to go to work’ This role would be filled by an oblique complement introduced by an adposition in English, as in the example below: (4) Other differences do not show such clear-cut contrasts between English and Naija, but are still interesting as they indicate areas which might need to be investigated further. We measure that 1.7 % of all dependency relations1 in the Naija treebank are labeled dislocated. The mean length of sentences being around 10 tokens, this means that on average there is a dislocation in 1 sentence out of 6, which is very significant, even more so when compared to the 0.0004% frequency found in written English.
Unfortunately our parser performs poorly on this relation
(due to the lack of training data) and no reliable frequency
count of this relation type can be extracted from the
spoken English corpus. We therefore look at spoken
French (which has the reputation of being particularly
prone to dislocations) to get a better sense of the
significance of our findings, and find that 1.0 % of
dependency links are dislocated
We might also be interested in the differences in distribution of part-of-speech tags3 between English and Naija.
Fig 1. Relative frequency of pos tags in English 2 One reviewer also noted that some of the English corpora such as EWT were automatically converted from constituent treebanks using rule-based systems which often fail to identify dislocated constructions. 3 We filtered tokens with PUNCT, X and SYM tags
Fig 2. Relative frequency of pos tags in Naija Naija has significantly more verbs while the English corpus is a lot richer in nouns. Part of the overrepresentation of verbs in Naija can be attributed to Serial Verb Constructions, with verbs in the second position representing 1.48 % of all tokens, but this account does not suffice to explain such a gap. Investigating this disparity, we also measured other relations involving verbal dependents such as ccomp. We find twice as many clausal complements with respectively 1.64 % and 0.82 % ccomp links in Naija and English. This indicates that looking at complex sentences in more details might provide us with additional examples of differences between the two languages.
We also expect that genre differences4 between the treebanks play an important part in this repartition. Future work using a Nigerian English corpus of both spoken and written texts should allow us to better determine the extent of differences due to genre and the variety of English being considered.
Interestingly enough, even though Naija allows the dropping of pronouns they are still very frequent in our corpus. One possible explanation is that pronouns are highly susceptible to repetition and reformulation in spoken language. But it might also have to do with the frequent topicalization of subjects through dislocation in Naija, as in (6), or with rhetorical devices which involve repeating the pronoun to emphasize parallelism as in (7). (6) dat man im pull over that man he pulls over ‘that man pulls over’ (7) dem go bring am dem go seize am again.
they will bring it they will seize it again ‘they will bring it and seize it again’ 4 There is a small portion of spoken English in UD_EnglishLinES, but apart from this the corpus we used is all written texts, with variations in terms of genres (news, wiki, nonfiction, blog, emails, legal texts..). The Naija treebank is all spoken texts (conversations and interviews). 5.
Annotators who were speakers of Naija reported that throughout the annotation process, their vision of Naija had changed. They noticed more readily that some syntactic phenomena were specific to Naija and that there were complex rules which governed the Naija grammar. We believe this to be an interesting pedagogical experiment where student annotators re-discover their language through the annotation of a corpus, and are confronted with regularities and patterns that sometimes went unnoticed in their day to day life (particularly so since speaking Naija is mostly depreciated).
We think that claims of Naija being a separate language can better be supported using a treebank. Indeed, while lexical differences are certainly noticeable between Naija and English, we believe that the identity of the language lies in its syntactic structure which is not as easily accessible from raw text or even tagged corpus. Having a treebank of Naija enables us to quantify the frequency of some syntactic structures, which in turns helps us to evaluate the complexity and idiosyncracies of the Naija grammar, and to measure the distance the language has taken from English. Comparisons between the two languages could also yield interesting insights concerning the ungoing creolization process of Naija.
We thank our reviewers for valuable remarks and corrections. This work is supported by the French National Research Agency (ANR) with the project NaijaSynCor