Monolingual and bilingual childre

Developmental differences between monolingual and bilingual children

The first language acquisition of infants is an astonishing and remarkable phenomenon on its own. It is unbelievable what knowledge these children can acquire in such a short period. There are certain cases, however, when these infants were born into bilingual families: that is, families where parents speak different languages. Bilingual children, thus, are the ones who need to acquire two languages simultaneously, studying both their mothers’ and their fathers’ mother tongues. This research aims to discover what developmental differences there are between monolingual and bilingual infants (if there are any) and what difficulties children have acquiring two different languages at the same time.

The first major difference between the two sides (apart from the amount of information they have to obtain) lays on the systemization of knowledge. Monolingual infants need to treat the sounds and expressions they hear as part of one united system. In contrast, bilingual infants need not only create a system between the things they are hearing and what they refer to, but they even need to separate and pigeonhole them into two different language systems. This is called ‘Language Discrimination’ and is a common phenomenon for all bilinguals.

Although in bilingual families, language teaching usually occurs in a one-person-one-language context (that is, each parent represents one language only in front of the child), there are several situations when a ‘neutral’ (previously unknown) person is talking to the infant. This can be the most difficult for the child, as they need to find the proper communicational channel without the familiar face, sound… etc. of the parents, which they usually connect the given language to. This can be said to be the first major difference between bilingual and monolingual infants. Not only need bilinguals learn twice as many words and structures as one-language children do, they also need to separate the inputs into two different systems.

There is another difficulty, with which monolinguals do not need to deal and that is ‘Code Mixing’. ‘Code Mixing’ “is the use of elements (phonological, lexical, morphosyntactic) from two languages in the same utterance or stretch of conversation. It can occur within an utterance (intra-utterance mixing-e.g., ‘see cheval‘ [horse]) or between utterances (inter-utterance mixing)” (Genesee & Nicoladis, 2007). This phenomenon is prevalent and typical for bilinguals, not only while they are children, but also among grown-ups.

In case of infants, code-mixing can usually appear in the form of gap-filling. This means that, while they are speaking in one of their native languages, they substitute certain words or phrases from the other language of theirs. This can be the result of incomplete language knowledge; but it can also derive from the fact that a given word does not come to the child’s mind and they substitute it for avoiding communicational breakdown. Code-mixing is based on the context-sensitivity of children; this means that – depending on whom they are talking to – they use one of their languages as dominant and only borrow inputs from the other system. (This can depend on which parent they are speaking with, for instance.) Since monolingual children have no other systems from which they can borrow resources, this phenomenon is not known for them; thus, only bilinguals face them.

The appearance of the first words is at about the same age by mono- and bilingual children alike. They occur at the age of 12 or 13 months. Further vocabulary acquisition (first nouns, verbs, expressions… etc.) also come – more or less – at the same time. However, there is a major difference between the two groups. When monolingual children learn a new word or expression, they connect it to a new referent. As opposed to this, bilingual children have more than one word for everything, thus, the new name does not necessarily comes with a new referent for them. “As a result, bilinguals’ total vocabulary size (total number of words) is different from their total conceptual vocabulary (the total number of nameable concepts). It remains unclear which of these measures is most comparable to simple vocabulary size measured in monolingual infants.” (Werker & Byers-Heinlein, 2008) This way or another, this is the reason why it is so difficult to contrast their vocabulary and word learning process.

Apart from the previously mentioned aspects, we need to cover two more important areas and these are children’s communicative competence and learning flexibility. There are certain problems which are relevant to monolingual and bilingual children equally: “production of target-like language forms that are comprehensible to others; getting one’s meaning across when language acquisition is incomplete; and use of language in socially appropriate ways” (Genesee & Nicoladis, 2007). Nevertheless, bilinguals also have to cope with the difficulties of conjugating a given situation with one of their languages, raising further hardships for them.

As for learning flexibility, one would assume that bilinguals learn much slower as they need to achieve more language knowledge during the same time. However, research by Ágnes Melinda Kovács and Jacques Mehler (2009) proved that “[t]welve-month-old preverbal bilingual infants […] seem to be more flexible learners of multiple structural regularities than monolinguals.” Therefore, the fact that they will later speak two native languages comes with a further advantage that they are (more) able to study two different things simultaneously.

Altogether, we can see that beside the similarities, monolingual and bilingual children have several differences, as well. The acquisition of two languages comes along with further difficulties – apart from the amount of knowledge they need to achieve – such as categorisation hardships, code-mixing and so on. Nevertheless, the process of acquiring two languages needs approximately the same amount of time as learning only one first language. First words and first expressions all appear at about the same age by both groups. In addition to these, beside the later advantages of knowing two languages, the developed learning flexibility of bilinguals will help these children in their later studies as well.


Genesee, F., & Nicoladis, E. (2007). Bilingual first language acquisition. In E. Hoff & M. Shatz (Eds.), Handbook of Language Development (pp. 324-342). Oxford, England: Blackwell.

Kovacs, Á. M., & Mehler, J. (2009). Flexible Learning of Multiple Speech Structures in Bilingual Infants. Science, 325. doi:10.1126/science.1173947

Werker, J. F., & Byers-Heinlein, K. (2008). Bilingualism in infancy: First steps in perception and comprehension [Electronic version]. Trends in Cognitive Sciences, 12(4), 144-151.