Early Lexicon of the Yoruba Child

This paper examines the lexicon of the Yoruba child at the initial stage. We examined the composition of the early lexicon of the Yoruba child and how they are acquired. The research is couched in the Minimalist Programme which believes that language acquisition is a matter of learning vocabulary and determining lexical idiosyncrasies. A quantitative analysis of the data is carried out. The database consisted of longitudinal studies of three children, Damilare, Temiloluwa and Tola, between the ages of fifteen (15) and thirty-six (36) months. We found that there were few lexical items which were gradually built up by the children. We also discovered that the first sets of words to be acquired are verbal items, followed by nominal items. The presence of transitive and intransitive verbs is noted in the utterances of the children and we conclude that the children make use of verbs related to actions and events that they or those around them are involved in.


Introduction
After discovering the meaning of certain words, the child has to determine the complex ways in which words are combined to form sentences; he has to determine the frame in which the words in the language occur.Hróarsdóttir (2003:116) says that evidence from human language studies shows that children learn very complex phenomena in a relatively short period of time during their first language acquisition.The aim of this paper is to examine the composition of early lexicon of the Yoruba child.What composes the early lexicon of the Yoruba child and how are they acquired?
According to Clark (2000:181) children naturally obtain a "communicative competence," intrinsically understand the rules of grammar, and gain knowledge of the rules of using language.Clark also believes that linguistic structure comes through the child's own cognitive and social activity.The lexicon is the human mental dictionary or list of words and their properties and one of the most important tasks that the children acquiring language face is the development of this lexicon.Lexicon development comes at the early stage of language development right from the pre-grammatical stage.
The lexicon is a part of the language faculty.It is the human mental dictionary or list of words and their properties.It is a set of grammatical objects formed by a subset of features out of the total set of features that are universally possible (Martinez-Ferreiro and Mata-Vigara 2007).Every piece of information about a word is stored in the lexicon.It contains the meaning of the word, the category, the pronunciation, exceptional information like morphological irregularities and the theta grid-the argument structure.Lofti (1999:10) sees the lexicon as a network of concepts and categories with some phonetic labels and formal features that characterize grammatical limitations on their use.The lexicon feeds the computational component.Developing the lexicon is an important step in language acquisition.The composition of children's early lexicon has been the object of much investigation.The need to know whether verbs or nouns come first in the child's early lexicon form the focus of most of these studies.At the initial stage, the lexicon is very few in number but gradually it is built up.The acquisition of lexical items helps to build the lexicon of the children.According to Stoll, Bickel, Lieven, Banjade, Bhatta, Gaenszle, Paudyal, Pettigrew, Rai, and Rai (2009), children's early vocabularies display a large variety of parts of speech, and a large range of functions with which various parts of speech are used (Bloom, Tinker, & Margulis, 1994;Gopnik, 1988;Nelson, 1973;Tomasello & Todd, 1983).This paper examines the order that the Yoruba child follows in the acquisition of lexical items.

Methodology
We examined the corpus of children's early speech.The data consist of a set of spontaneous longitudinal speech of children produced during interactions with parents, siblings, caregivers and other family members.The data is collected from three children, Damilare, Temiloluwa, and Tola who were recorded at home from 18 months to 36 months.Damilare is the first child of educated middle class parents.The parents live and work in Ilorin, the Capital City of Kwara State, Nigeria.The data presented for him covers a period of fifteen (15) to thirty-six (36) months.The data were collected by the mother (the researcher) on a daily basis.Damilare's data consist of questions, responses and utterances between him and the parents and other members of the family.It also included his utterances while playing alone.We could safely say that the exercise made it possible to know at each point he has acquired anything linguistically significant.The best form of longitudinal data collection should be between a child and any of the parents or someone who lives with the family.This enables close interaction with the child which aids easy data collection.This also removes most possible constraints that may arise.Temiloluwa and Tola are a set of female twins of educated middle class parents.The parents live and work in Ilorin.They have two older siblings, a brother and a sister.The data presented for them in this study cover from fifteen (15) months to thirty-six (36) months.The data were collected by their father daily at home and in other possible situations.The data consist of utterances, responses, questions between the two of them, with their parents and siblings and other members of the family.
A quantitative and qualitative analysis of the data was carried out.The quantitative analysis uses simple mathematical calculations with the aid of tables and charts.The tables show the percentage of observed phenomena.The charts consist of bar charts drawn from the tables.The bar charts are used to show comparison between different items at a particular point in time.

The Lexicon and Minimalist Programme
The Minimalist Programme is the model on which this paper rests.The model of grammar used in accounting for child language acquisition must be one which allows for generalization and predictions within a comprehensive and unified theory of language (Kessler 1971:3).The programme adopts minimalism or simplicity to achieve descriptive adequacy and explanatory adequacy.Language acquisition within the Minimalist Programme is seen as a matter of learning vocabulary, we all speak the same language differing only in vocabularies (Cook, 1996).According to Chomsky (1995:131) there is only one human language, apart from the lexicon, and language acquisition is in essence a matter of determining lexical idiosyncrasies.The programme, according to Longa and Lorenzo (2008:541) 'redefined the meta-theoretical role of the theory of acquisition within generative grammar'.Radford (2000:1) states that "the revised model of Minimalism presented in Chomsky (1998Chomsky ( , 1999) ) raises interesting questions about the nature of language acquisition."Chomsky (1999:7) says that the Language Faculty specifies a universal set of features; these features the child acquiring language has to learn.The major task, therefore, facing the child acquiring the syntax of his language is assembling features into lexical items.Language Faculty is a set of procedures or programme which all human beings possess.It is required for the acquisition of the grammar of languages (Radford 2004).Radford (2000) examines child language from the minimalist perspective.He sees the child language as being perfect.Radford believes that innate architectural principles determine the nature of children's initial grammars.He argues that a perfect grammar would project a given formal feature only when necessary.He concludes that even though adult languages are imperfect systems, the acquisition process itself is perfect as it maximizes perfection.He also states that the initial grammars developed by children are perfect (Radford 2000:13).
The minimalist hypothesis, according to Uziel-Karl (2001), is that UG provides children with full knowledge of phrase structure right from the start, but at each point in the process of acquisition, they construct the smallest convergent trees that their grammar requires, based on the evidence at their disposal.Wilson, Fox and Pascoe (2008:2) believe that in the Minimalist model, the lexicon plays a greater role in the grammar than in earlier models of generative grammar, according to Amfani (2006:162) analysis begins in the lexicon in the Minimalist Programme.The reason is that in the Minimalist approach words emerge fully derived with their inflectional features, verbs and nouns are taken from the lexicon fully inflected.Since the lexicon is made up of lexical items, we will examine the acquisition of verbal items, transitive and intransitive verbs and nominal items will be examined in the following subsections.

Acquisition of Verbal Items
The verb constitutes a universal and very important lexical category (Robins 1966, Hopper & Thompson 1984, Langacker 1987, Uziel-Karl 2001).Awobuluyi (1979:114) says that verbs play a central role in sentences and that they are almost always present in sentences.Verbs could be regarded as the most important part of the sentence; they are a necessary component of all sentences.A verb is defined by the semantic roles that it "takes", i.e. its case frame.This means that the lexical entry of a verb directly determines its syntactic behaviour (Lin, 2004:15).
The verb is the backbone of the sentence.Verbs name events or states with participants, making them the organizational core of the sentence, so their meaning is key to sentence meaning (Levin 2007:1).Verbs also describe relationships and organize sentences with argument structure (Scherf, 2005).Verbs could be classified into one-place predicates, two-place predicates or three-place predicates, on the basis of the number of arguments they take (Haegeman 1994:41).These are traditionally referred to as intransitive, transitive and ditransitive verbs, respectively.A verb is either transitive or not depending on the type of action or state it expresses from its meaning.Verbs are majorly classified according to the types of complements they select.
Verbs especially play a very important role in language structure, in linguistics form-function relations, and in processes of language acquisition and language development (Uziel-Karl 2001).The child that is acquiring Yoruba will have to learn the syntactic category of words in the language and also more importantly learn the sub-categorization of verbs in the language.
We assume that the first sets of lexical items the child acquires are verbal items.To test these claims we examined the early verbs of Damilare and Temiloluwa from the one word stage to the early multi-word stage when they have started to merge items.The boundary for this stage is set at twenty-four (24) months i.e. two years.By this time, the naturalistic speech of the children has turned complex.The children moved from the one stage to the early word combination stage in the course of the taking the samples.For example: In order to find the percentage of verbal items for each of the children, we counted the number of all the lexical items and then find the percentage of verbal items from the sum total of all lexical items i.e. the number of verbal items divided by the total number of lexical items multiplied by hundred as indicated below.

Total Number of Lexical Items 1
To find the percentage of other lexical items, we counted the number of other lexical items and then find their percentage from the sum total of all lexical items i.e. the number of other lexical items divided by the total number of lexical items multiplied by hundred.

Other Lexical Items 100
Total Number of Lexical Items 1 We did not just subtract the percentage of verbal items from other lexical items or vice versa because we needed to be sure that every lexical item is accounted for.The tables below show the distribution of verbal items vis-à-vis other lexical items in the early utterances of Damilare, Temiloluwa and Tola respectively.From the tables above, verbal items in the speech of Damilare was 53% at sixteen ( 16) months and reduced to 41.3% at twenty-three (23) months.In the speech of Temiloluwa, 47.8% of verbal items were recorded at sixteen ( 16) months and reduces to 27.6% at twenty-three (23) months.For Tola, her verbal items were 42.1% at sixteen ( 16) months and 28.4% at twenty-three (23) months.From the tables above, we see that verbs constitute the first set of lexical items to be acquired.We could also deduce that the use of verbal items is high in their utterances.The reason for this is not far-fetched.The child at this stage just wants to make his needs known.This is achieved by simply using the verb which to a large extent serves his or her purpose.The examples that follow present some verbs in the utterances of the children.

Transitive and Intransitive Verbs in the Early Sentences of the Yoruba Child
Yoruba verbs can be broadly divided into transitive and intransitive verbs.Transitive verbs require two arguments; the subject and the object of the verb while intransitive verb has only one argument, the subject.Some previous studies claim that intransitive verbs are easier to produce thereby easily acquired because they do not require direct object argument (Valian 1991) while some believe that the transitive verb is easier to produce than intransitive verbs (Tomasello and Brooks 1998).Choi (1999) discovers that Korean children use more of transitive verbs at the early stage while Fukuda (2005) finds that Japanese children's early verbs are more of intransitive verbs.Fukuda and Choi (2006) in their own investigation conclude that both Korean and Japanese children produce more intransitive verbs.They suggest that children use more intransitives because it encodes a single participant and are cognitively less complex than events with two or more participants.This section seeks to know the order of acquisition of transitive and intransitive verbs and whether one is more basic than the other.Table ( 4) below shows the distribution of the first set of twenty verbs in the early speech of Damilare, Temiloluwa and Tola.The verbs in bold are transitive verbs while the italicised verbs are intransitive verbs.We can see that the first three verbs are transitive verbs.However, there are eleven intransitive verbs as against nine transitive verbs in that distribution.Table 5 shows in percentage, the distribution of order of acquisition of transitive and intransitive verbs by the three children.The results as shown in the table show a higher percentage of usage of transitive verbs than intransitive verbs.At seventeen (17) months, Damilare records 57.7% transitive verbs against 38.5% intransitive verbs while Tola records 50% transitive verbs and 33.3% intransitive verbs.Temiloluwa, however records 33.3% transitive verbs and 52.8% intransitive verbs.This is the only time that intransitive verbs are higher than transitive verbs in her utterances.At twenty-three (23) months, Damilare has 58.6% transitive verbs and 41.4% intransitive verbs; Temilouwa has 72% transitive verbs and 28% intransitive verbs while Tola records 70% transitive and 30% intransitive verbs respectively.This is further illustrated in figure 1 below.
Figure 1.Transitive and Intransitive Verbs in the Early Sentences of Temiloluwa From the distribution above, we could see that there is a good representation of the two types of verbs at all stages of acquisition.We cannot therefore categorically say that transitive verbs are acquired before intransitive verbs or vice versa.We can say that these early verbs are those related to actions and events that the children or those around them are involved in.

Acquisition of Nominal Items
The other major lexical items used by the child are the nominal items.Bamgbose (1967:8) defines a noun as 'a word which can occur independently or with qualifiers in the nominal group' while Stockwell (1977:48) defines it 'as symbols for entities, abstract or concrete, countable or uncountable (mass), animate or inanimate, human or non-human, etc. Nouns are classified into the classes of animate, inanimate, concrete, abstract, countable and uncountable nouns.
Cross-linguistic studies have expressed the importance of nominal items in the early speech of children In order to find the percentage of nominal items for each of the children, we counted the number of all the lexical items and then find the percentage of nominal items from the sum total of all lexical items i.e. the number of nominal items divided by the total number of lexical items multiplied by hundred.

Total Number of Lexical Items 1
We did same for other lexical items.Tables 6, 7, and 8 present a paradigm of the acquisition of nominal lexical items vis-à-vis other lexical items by the three children.From these tables, we discover that nominal items, apart from verbs, also constitute one of the first sets of items acquired by the Yoruba child.We could also see that they constitute a high percentage of the children's utterances.Nominal items range from 45.8% to 50.8% in the speech of Damilare while in Temiloluwa's speech, 34.04% of nominal items were recorded at sixteen ( 16) months and 41.5% at twenty-three (23) months.For Tola, 36.8% nominal items were recorded at sixteen ( 16) months and 34.3% at twenty-three months.We could safely deduce that at the early stage, that they make use of verbal items more than nominal items.In order to find the percentage of verbs for each of the children, we counted the number of all the lexical items and then find the percentage of verbs from the sum total of all lexical items i.e. the number of verbs divided by the total number of lexical items multiplied by hundred.

Verbs 100 Total Number of Lexical Items 1
To find the percentage of nouns for each of the children, we counted the number of all the lexical items and then find the percentage of nouns from the sum total of all lexical items i.e. the number of nouns divided by the total number of lexical items multiplied by hundred.

Nouns 100
Total Number of Lexical Items 1 We did not just subtract the percentage of verbs from nouns or nouns from verbs because there are some other lexical items that make up the utterances of the children.Table 9 below shows the occurrence of nouns and verbs in the utterances of the children.By 21 months, Damilare's nouns stand at 48.6% as against 41.3% of verbs.By 23 months, Damilare's nouns have moved to 50.8% while his verbs stand 47.7%.At the same age (23 months), Temiloluwa's nouns stand at 41.5% and the verb at 27.6%, while the percentage of Tola's nouns is 34.3%, her verbs stand at 28.4%.The reason for this change is because at this stage, which is from the two-word stage to the multi-word stage, the sentence of the Yoruba child just like that of the adult has only one verb while there may be more than a noun in an utterance, depending on the realization of arguments.

Conclusion
We found that there were few lexical items which were gradually built up by the children.We discovered that the first sets of words to be acquired are verbal items, followed by nominal items.The statistical representations above show the growth and decline of some features.For example, figure 2 above shows a higher usage of verbs between sixteen (16) months and twenty (20) months while from twenty-one (21) months upwards, the usage of nouns is higher.It shows that the children keep processing the input data available to them in order for them to arrive at adult linguistic competence.The presence of transitive and intransitive verbs is noted in the utterances of the children and we conclude that the children make use of verbs related to actions and events that they or those around them are involved in.
We also discovered that as the children grow there is a decrease in the number of utterances without verbs.This shows that their language is developing normally.Arokoyo (2010:173) relying on cross-sectional data concludes that Yoruba children from thirty-six (36) to sixty (60) months have acquired a lot of language skills and can use language very productively Every lexical category is represented fairly in their speech.In fact at this stage, they have a proficiency that is close to that of the adult.
Taking a careful look at the data, it was discovered that from the very few words that the children acquired at the initial state when they could not even pronounce the words properly and do not even know the meaning of most of the words, they grow to have very good knowledge of the words in their language.With the development of the lexicon of the children there is an increase in their proficiency and by implication their linguistic competence.They moved from different stages of language acquisition until they acquire adult linguistic competence.

Figure 2
Figure 2 displays the distribution of Nouns and Verbs in the speech of Damilare:

Table 1 .
Distribution of Verbal Items in the Early Utterances of Damilare

Table 2 .
Distribution of Verbal Items in the Early Utterances of Temiloluwa

Table 3 .
Distribution of Verbal Items in the Early Utterances of Tola

Table 4 :
First Set of Verbs in the Early Speech of Damilare, Temiloluwa and Tola

Table 5 .
Transitive and Intransitive Verbs in the Early Sentences of the Yoruba Child

Table 6 .
Distribution of Nominal Items in the Early Utterances of Damilare

Table 7 .
Distribution of Nominal Items in the Early Utterances of Temiloluwa

Table 8 .
Distribution of Nominal Items in the Early Utterances of Tola

Table 9 .
Distribution of Nouns and Verbs in the Early Utterances of Damilare, Temiloluwa and Tola