Study of LANGUAGE ACQUISITION made easy: our beginner’s guide explores the 4 key sub-fields. Start learning today!
Table of Contents
- INTRODUCTION: The importance of the science of language learning and development
- The construct of LANGUAGE and the different sub-fields of LANGUAGE ACQUISITION
- 1. First Language Acquisition
- 2. Second Language Acquisition
- 3. Third Language Acquisition
- 4. Bilingual Language Acquisition
- Conclusion: What are your beliefs about language development?
- Recommended Readings
- References
INTRODUCTION: The importance of the science of language learning and development
Half a decade ago, I made the decision to pursue a Master’s programme in “applied linguistics”. My main motivation then, was rooted in the study of LANGUAGE ACQUISITION within the broader context of bilingualism and multilingualism.
In hindsight, this was by no means coincidental, as I have always been curious about many questions related to the study of language acquisition. As a practising teacher back then, I have been fortunate to have ample opportunities to engage in teacher-fronted action research. Those projects in which I have been involved were generally focused on tailored interventions targeted at a particular profile of learners in my school then.
However, as I reflected on those learning, something appears to be lacking. While the practice-oriented research has its place in my operating context then, what I yearned further was a deeper understanding of the learning sciences pertaining to language learning and development – a more well-framed theory of language acquisition.
To me, embarking on the journey of understanding language acquisition is akin to unlocking the secrets of the human mind itself. Human language is such a fascinating construct and our comprehension of its emergence in the mind should not be predicated on personal anecdotes or professional intuition. Instead, it should be established on a solid foundation of knowledge obtained through rigorous scientific inquiry.
And so, this beginner’s guide is targeted at those among us who have recently started our journey of language education or have developed a newfound interest in this area (like I did half a decade ago). I aim to present the most salient points that any beginner should be aware of as we embark on our study of language acquisition.
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The construct of LANGUAGE and the different sub-fields of LANGUAGE ACQUISITION
To begin, I have to highlight the multi-faceted construct of “language” again – that it is not unitary and has a group of possible definitions. In that sense, LANGUAGE ACQUISITION is not just simply about learning grammar; it actually encapsulates several disciplines such as psychology, linguistics, anthropology, neuroscience, and more.
The interdisciplinary nature of the field is what fortifies its robustness in answering questions from many different aspects and adds on to its credibility especially when findings triangulated across different disciplines suggest similar conclusions.
That being said, when exploring research related to language acquisition, we often focus on the target language(s) – be it a first, second, third language, or multiple languages concurrently. Henceforth I’d provide an overview into the definition of each, the key questions and notable insights that can inform our practice.
1. First Language Acquisition

1.1 Definition
If unspecified, the term “LANGUAGE ACQUISITION” in research is also taken to be synonymous with “FIRST LANGUAGE ACQUISITION”, which refers to the process by which children learn their first language (L1) or native language. As such, it is also known as “child language acquisition”.
L1 acquisition is a remarkable process that occurs naturally and generally without formal instruction (Hummel, 2014; Saville-Troike & Barto, 2017; VanPatten & Benati, 2015). As children are exposed to the language spoken by their caregivers and the surrounding environment, they gradually develop linguistic competence or linguistic knowledge in this language. We usually see this language becoming the L1, although controversies can exist upon certain trajectories in development of the language (for more discussion on such controversies, you might want to find out the difference between the first language and second language).
1.2 Key lines of inquiry
And so, the study of First Language Acquisition emerged as a field that purposes in examining the emergence of the language faculty within children, or more broadly in humans in general. With that in mind, below is the list of questions that L1 Acquisition scholars study (Clark, 2016; Foster-Cohen, 2009; Lust, 2006; Rowland, 2014):
- When does language acquisition start? How does it start? What mechanisms need to be in place?
- What is it about the human mind that makes it possible to acquire language? Is there a language acquisition device in place?
- To what extent is the language faculty biologically programmed? Which aspects are hardwired as part of the human mind?
- Is there a “critical period” for L1 acquisition? If so, how long is this period and when does it end?
- What is the specific linguistic knowledge gained by the children at different stages? How do they develop the grammar? At which period and under what conditions do they develop certain aspects of the grammar?
- How do children transition from the initial stages of language development to more advanced linguistic abilities?
- Are there universal stages or patterns in the acquisition of sounds, words, and grammatical structures across different languages?
- How do children learn language beyond the finite data presented to them in the given input to gain a representation of the target grammar?
- What factors contribute to individual differences in the rate and success of first language acquisition?
1.3 Key relevant insights
In general, if we are interested in how children acquire language or how language learning should be like at the elementary levels (e.g. K – Grade 4), or that we are working with children learning their L1(s), the key insights here should be very relevant for our practice.
1.3.1 Language development starts before the child is born.

Language development starts before the child is born through the process of prenatal exposure to speech sounds. The foetal brain is well equipped to process human speech sounds, and research suggests that babies can perceive and recognize certain aspects of language while still in the womb, and form memories of these experiences (Saxton, 2017; Sebastian-Galles & Santolin, 2020). These early experiences and exposures lay the foundation for further language learning and acquisition after birth. So, those among us as parents should aim to speak to our children even before they are born.
1.3.2 Language input is essential for learning and acquisition.
Input plays a crucial role in L1 Acquisition. It includes the language spoken by caregivers and the surrounding environment, provides children with the necessary exposure to phonetic, lexical, grammatical, and pragmatic aspects of the language. Children who do not receive enough exposure due to dire circumstances, such as the classic case of “Genie”, do not eventually acquire a language like their peers (Hummel, 2014; Rowland, 2014).
There are debates though, as to the degree of importance – such that whether input is merely a trigger to activate the innate knowledge encoded in the child’s genes or that input is the driving force for learning as it forms the data premise on which the child detects patterns for learning (Ambridge & Lieven, 2011; Foster-Cohen, 2009; Lidz & Gagliardi, 2015; Lust, 2006; Rowland, 2014). Regardless of either, it is generally agreed that language input with the necessary characteristics facilitates language acquisition – this is something tangible for us to work with.
1.3.3 L1 Acquisition involves considerable ingenuity and active participation from children.

Research shows that language acquisition involves considerable ingenuity and active participation from children through various observations and studies (Ibbotson, 2022; Saxton, 2017). Children demonstrate their active role by going beyond mere imitation of the language they hear – they are not passive recipients of language input. They engage in processes such as generalisation, pattern extraction, and error production (thus over-generalisation), which provide insights into how they learn and construct language. And thus, we know that we should try to facilitate such participation instead of inhibiting it (e.g. normative strong-person enforcement of silence in the classrooms).
1.3.4 L1 Acquisition can demonstrate a U-shaped learning curve.
Within L1 Acquisition, the U-shaped learning curve refers to a phenomenon where children initially produce a correct form, then over-generalise a rule and produce an incorrect form, and eventually return to using the correct form again. This pattern can be seen in various aspects of language acquisition, such as the acquisition of irregular past tense forms (Hummel, 2014). As such, we should not be too alarmed when we see our young children “regressing” as this can be a typical phenomenon of over-generalisation as our learners are restructuring their language systems.
1.3.5 Fundamental milestones are reached at similar times regardless of the specific language being learned.
People used to ask whether specific languages may result in different trajectories of language development (some of my colleagues still hold on to such a hypothesis). What I present as a key finding is that, children typically attain certain key fundamental achievements at similar ages or timeframes, regardless of whether they are learning English, Spanish, Mandarin, or any other language (Saville-Troike & Barto, 2017; Sebastian-Galles & Santolin, 2020).
Here, what I am qualifying as milestones include important aspects of language development, such as the emergence of babbling, the production of first words, the development of two-word combinations, and the acquisition of more complex grammatical structures. Of course, a child acquiring L1-English is not expected to discriminate meanings using tonal information as in L1-Mandarin. What is highlighted here is that there are universal patterns and sequences when children learn a language, that are independent of the specific language being acquired.
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2. Second Language Acquisition

2.1 Definition
SECOND LANGUAGE ACQUISITION, or usually truncated as SLA, refers to the process of learning additional language(s) after at least a L1 has been acquired (Gass, Behney & Plonsky, 2020; Sadeghi, 2022; Saville-Troike & Barto, 2017; VanPatten & Benati, 2015). While the modifier “second” implies a single language that comes in chronologically second, identification of second language(s) or L2s in research may be operationalised otherwise.
For instance, individuals exposed to more than one language in early childhood may have more than one L1 (e.g repertoire of three languages for multilinguals), thus any single additional language learned after that cannot be second by strict definition.
Also, within majority of research studies, there is no specific distinction made between any additional language learned after the initial L1(s) have been acquired. Any subsequent language, regardless of whether it’s the second, third, fourth, or nth, is considered an L2(s) as long as it is acquired after a L1 system is already in place. You can read further here for more discussions on how a L2 is different from a L1.
Notably, some scholars do make a distinction between a L2 and a foreign language (FL) usually to distinguish the learning contexts of the language especially within formal instruction. For majority of other studies, especially when it comes to understanding the psycholinguistic aspects of learning additional language(s), a L2 is taken to be synonymous with a foreign language.
2.2 Key lines of inquiry
Studies on SLA usually focus on how learners create a new language system where there is/are existing L1 system(s) in place. Learners, in this aspect, can refer to both young children, adolescents or adults. Taking these into account, below is the list of questions that SLA scholars study (Gass, Behney & Plonsky, 2020; Hummel, 2014; Sadeghi, 2022; Saville-Troike & Barto, 2017; VanPatten & Benati, 2015):
- What is the initial state of learners who start acquiring a L2? How do they move from the initial state to their state of ultimate attainment?
- What factors influence the process of acquiring a L2?
- How do learners develop proficiency in a L2, and what are the stages of development?
- What is the architecture and characteristics of the interlanguage(s) (i.e. the dynamic and transitional grammar represented by the L2 learners of the target language)?
- What role do various types of L2 input and output play in SLA? What are the factors governing the use and the degree of the use of L2 input and output in SLA?
- Why do most L2 learners not attain native-like competence and proficiency? Can they possibly do so, and if so, under what conditions?
- Is there a critical period for L2 Acquisition? How is it different or similar to L1 Acquisition?
- How does instruction impact L2 Acquisition, and what are the most effective teaching methods?
- What are the differences and similarities between L1 Acquisition and L2 Acquisition?
- How do individual differences, such as age, aptitude, and motivation, affect L2 Acquisition?
- What are the cognitive processes involved in L2 Acquisition, such as memory, attention, and problem-solving?
2.3 Key relevant insights
Judging from previous interactions on LEA, I believe most of us would be most interested in SLA studies. Those among us who work with learners in bilingual or multilingual contexts, or in a setting where our target language is identified as a L2 or FL, we benefit a lot from these insights on the processes, challenges, and strategies involved in learning a L2.
2.3.1 L2 learners experience large variability in success in contrast to L1 Acquisition.

While it is generally observed that all children will develop full competence of their L1, regardless of target language, given all the typical conditions (e.g. not socially deprived like “Genie”), the same cannot be said of L2 learners. Most L2 learners would hit a plateau of learning where no improvement is further achieved (also known as fossilisation), while only a minority does go on to achieve native-like competence (or rather more akin to L1 users) (Gass, Behney & Plonsky, 2020; Hummel, 2014; VanPatten & Williams, 2015). This can be sobering for us as L2 educators, to know the realistic limits of pushing our learners to the peak of excellence. Of course, it does not preclude the possibility even if such a group is small.
2.3.2 Much of SLA happens incidentally and there is a limit to what L2 instruction can do.
Incidental language learning refers to the acquisition of language knowledge and skills that happen unintentionally while engaging in other activities, such as reading, listening to conversations, or watching movies (Sadeghi, 2022; VanPatten & Benati, 2015). This type of learning is often characterized by implicit learning processes, where learners absorb language patterns and structures without conscious awareness. It is observed that the bulk of SLA happens under such conditions, as opposed to formal instruction.
Let’s not get disappointed (I believe most of us are involved in classroom instruction). What this suggests is not that L2 instruction is obsolete: The merits of L2 instruction lie more in its provision of valuable guidance, practice, and structured learning opportunities. The awakening pill for us is just that L2 instruction alone is not sufficient to fully develop language proficiency – we need to exert influence on the general linguistic environment of our learners beyond our lessons, or on our partners (e.g. parents, stakeholders) and learners to create a conducive environment for L2 learning.
2.3.3 L2 learners would benefit from different types of language input and input of various characteristics.
Actually, one of the key insights would have been that L2-input is essential for L2 Acquisition. However, I do think that this is already taken to be the basic assumption for many of us, and that we are more concerned about the quantity and quality of input instead. In noting that much of SLA happens incidentally, then we should know that supporting learners with various types of input and input of different characteristics would be important. A more thorough discussion of such implications and tips where we can employ can be found in two other related articles on LEA: 7 Types of Language Input that can facilitate Language Acquisition according to research; and The Language Input Blueprint: Managing 9 Key Language Input Characteristics for Accelerated Language Learning (Bonus – Expert Tips included).
2.3.4 Individual differences modulate the outcomes of SLA quite significantly, although the degree to which that happens is still under investigation for many factors.
Individual differences have a significant impact on the outcomes of SLA, across various aspects of language learning (e.g. ultimate attainment, learning rates, pronunciation and accent, lexicon size) (Saville-Troike & Barto, 2017; VanPatten & Benati, 2015). Such individual differences include (but not limited to) age, language aptitude, motivation and attitudes, learning strategies, emotions and personality traits. The understanding of such differences may help us in identifying the pain points with some of our learners and devise targeted strategies accordingly to enable them to develop the necessary language skills.
2.3.5 There are age effects in SLA, but the existence of a critical period is largely challenged.

There is substantial evidence suggesting that attaining native-like competence like a L1 user is generally out of reach for most adults in learning the L2, though not completely impossible, in contrast to younger learners. However, much of this applies only to phonological accuracy (e.g. accent that are more akin to L1 users) and arguably parts of syntax (please note that this is highly contested) (Saville-Troike & Barto, 2017; VanPatten & Benati, 2015). This is important for us (and our learners) to counter the myths that adult learners can never be good in attaining L2 proficiency while also remaining cognisant not to place unrealistic expectations in their learning outcomes.
Notwithstanding such, the argument that a critical period (e.g. existence of a threshold age or period) exists for L2 Acquisition has been widely disputed in recent years, with the tendency to move towards the notion of a “sensitive period” (also contentious, as it may not be a language-specific faculty) in replacement. In a sense, parents and policymakers among us should take note of this not to dilute or de-prioritise L2 learning just because a certain age has been reached.
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3. Third Language Acquisition

3.1 Definition
Earlier when I wrote that any additional language learned after the L1(s) is regarded a L2, some of us may raise eyebrows and argue that learning an extra language with just one primary language differs from learning a third language when one already knows two languages (L1 and L2). Such is the argument of a group of scholars, which thus contributed to the growth of a collection of studies aiming to investigate such intricacies within Third Language Acquisition.
As a definition, THIRD LANGUAGE ACQUISITION (TLA) refers to the process of acquiring an additional language when an individual has at least 2 languages in his/her linguistic repertoire (Cenoz, 2013; De Angelis, 2007; Hammarberg, 2009; Hammarberg & Williams, 2009; Slabakova, 2017). In a sense, TLA can refer to the learning situation when an individual is learning an additional language after he/she has acquired a L1 in early childhood and learned a L2 later in life; and may also refer to the situation where the individual is an early bilingual (i.e. acquired two L1s in early childhood) and is learning a third language (L3).
Now we might wonder: I have spent lengths earlier to highlight that a L2 can denote any additional language, regardless of chronological sequence, that is learned after the L1 system(s) is/are in place, so why is TLA contradicting that? So are there studies on L4, L5 or L-n Acquisition?
The value proposition of TLA is that it aims to account for the cross-linguistic influence from more than one language in the acquisition of a new language when SLA tends to focus specifically on the additional language in relation to a single L1. Furthermore, L3 learners are usually hypothesised to possess different cognitive and metacognitive strategies compared to learners acquiring a L2 for the first time, since L3 learners have already developed strategies when they learn their preceding L2. TLA studies aim to investigate the influence of such hypotheses.
In any case, we need to understand that TLA is a relatively new area of research when compared to SLA. Also, SLA studies may also overlap with TLA when they factor in a wider repertoire of languages within the study or adopt definitions of L2(s) as what I have presented earlier. I am obliged to highlight too, that TLA or L3 Acquisition is the limit, in the sense that there is no further body of research on L4, L5 or L-n Acquisition.
3.2 Key lines of inquiry
TLA offers important insights into how learners make connections and comparisons between the languages they already know and the new language they are acquiring, both consciously and sub-consciously. While some key research questions may coincide with questions found in SLA, some of them are uniquely TLA issues (Cenoz, 2013; De Angelis, 2007; Hammarberg, 2009; Hammarberg & Williams, 2009; Slabakova, 2017):
- How does the acquisition of a L3 differ from the acquisition of a L2?
- What factors influence the success and outcomes of L3 Acquisition?
- How does prior knowledge of multiple languages impact the acquisition of a L3? How do knowledge and skills from L1 and L2 influence the acquisition of the L3?
- How do cognitive and psychological factors interact with the acquisition of a L3?
- What are the effects of language learning experience on L3 Acquisition?
- Do learners use different strategies for L3 acquisition compared to L2, and how effective are these strategies?
- How do typological characteristics of languages within the repertoire influence the acquisition of a L3?
- How does the interlanguage of the L3 evolve, considering the influence of L1 and L2?
3.3 Key relevant insights
TLA studies would be of particular interest to language educators working in multilingual contexts, where the target language that you are working on is an additional language to learners with at least two languages in their repertoire. That being said, TLA is not exactly a body of research that has a rich history like L1 and L2 Acquisition. I am a bit hesitant to share many inconclusive findings here, so the key insights are not really “facts” per se, but the directions that findings are pointing us to.
3.3.1 The process of learning a L3 can be influenced by the linguistic knowledge acquired from both the L1 and L2.
Such an “influence” refers to the cross-linguistic transfers that set the premise for the inception of TLA as a body of research. Transfers can either positive or negative, depending on whether it aids in the representation of the target L3 grammar according to the norms of the L1 users of the target L3.
The trend in TLA research is to identify whether the L1 or L2 exerts a larger influence on transfer(s) (De Angelis, 2007; Hammarberg & Williams, 2009; Saville-Troike & Barto, 2017). At present, the answer to this seems contingent on the following factors: relative proficiency in the L2 (the better the L2, the more possible it is translated into the transfer mechanisms); linguistic distance between the languages involved (e.g. how relatively similar is the L3 to the L1 and L2); the component of the language system (e.g. phonological influence tends to come from L1). Insights from such studies do help us in analysing the performance of our learners and formulating follow-up approaches based on formative assessment results.
3.3.2 Bilinguals/Multilinguals generally have an advantage over monolinguals in learning the same additional target language.
Research has largely demonstrated that individuals with multilingual backgrounds tend to excel in learning further languages (Cenoz, 2013; De Angelis, 2007). This advantage has been attributed to enhanced metalinguistic awareness, the development of effective language-learning strategies and cognitive flexibility.
That being said, scholars have highlighted that such an advantage is only more evident in cases of additive learning (as opposed to subtractive learning), in the sense that the L3 learning is not at the expense of the already acquired L1 and L2 (or L1s). Also, literacy seems to have a role in fine-tuning the extent of the advantage, such that literacy in the languages already acquired is correlated with a superior performance in acquiring the L3. What this means for us (and many learners) is that bilingualism should be recognised as an invaluable asset and literacy should be part of the equation in learning.
3.3.3 As an emergent finding, the more languages one knows, the more substantial the influence of prior linguistic knowledge on the acquisition of a new target language.
Some researchers have observed that individuals with a more extensive linguistic repertoire (e.g. more languages already learned) tend to experience a more pronounced positive impact on learning a target L3 language (De Angelis, 2007). One possible explanation is that learners have a wider range of linguistic experiences and structural possibilities to draw from in learning a new language. This is something that I must highlight to be emerging, thus not taken to be conclusive as yet, but it is indeed an important direction for future inquiries.
4. Bilingual Language Acquisition

4.1 Definition
Till this point, while there are fine distinctions in the different subfields, studies in L1, L2 or L3 acquisition tend to focus on only a single target language irrespective of learners’ existing linguistic repertoire (e.g. acquisition of L1-Spanish, acquisition of L2-Mandarin, acquisition of L3-German).
For studies in Bilingual Language Acquisition, however, there is more than one target language. In general, Bilingual Language Acquisition (BLA) refers to the process of acquiring and developing proficiency in two languages simultaneously or successively (but close in time frame) (Buschfeld, Ronan & Vida-Mannl, 2023; Sebastian-Galles & Santolin, 2020). It involves individuals who grow up in bilingual environments or who are exposed to and learn two languages from an early age.
As a disclaimer, BLA do consider more than two languages where necessary – the “bilingual” modifier here typically just imply “more than one”. However, we should also be realistic to note that most studies tend to focus on two though. Also, BLA does not typically deal with adults, even though adults can (of course!) learn more than one language simultaneously as L2s (or L3s).
4.2 Key lines of inquiry
The closest sibling of the few sub-fields to BLA would be L1 Acquisition, as both concerns the acquisition of languages in early childhood. However, L1 Acquisition studies tend to focus on only one L1 (though it may be possible that targeted subjects are acquiring another L1 but not considered or studied) while BLA studies all (at least two) of the languages at the outset. As such, we can see how scholars have shaped the key research questions uniquely for this sub-field (Bialytsok et al., 2009; Buschfeld, Ronan & Vida-Mannl, 2023; Pearson, 2009; Sebastian-Galles & Santolin, 2020; Yip & Matthews, 2022):
- How does BLA differ from monolingual language acquisition? What are the cognitive and linguistic constraints or benefits of BLA in particular?
- How much do bilingual individuals differ in the way they acquire and use grammar compared to monolingual individuals in the context of BLA?
- How does BLA differ from later SLA?
- Does a bilingual/multilingual child develop both or more languages as a single system or two (or more) separate systems? Do interactions between languages in the repertoire facilitate or impede comprehension and production?
- How do bilingual infants and children navigate between their two languages and develop language proficiency in both? How do they switch between languages, intentionally or unintentionally?
- What is the impact of BLA on metalinguistic awareness and language processing?
- What are the factors that contribute to successful BLA?
- How does BLA inform our understanding of language development and language learning processes?
- How much input is required from each target language in BLA for a child to become bilingual or multilingual? What qualities are required for the input?
4.3 Key relevant insights
Those among us that work with young bilinguals/multilinguals who are striving to learn two or more languages or young learners learning languages in bilingual education settings would benefit from the insights gained in studies on BLA. Arguably, if we are working with young learners, we might just want to keep tabs on BLA studies too, especially that societal bilingualism/multilingualism (even as a passive recipient) is more of the norm rather than the exception.
4.3.1 Bilingual children generally follow a similar course and rate of development in each language as monolingual children in various aspects, though the exact development may be modulated by a few factors.
Research shows that bilingual children generally reach important language milestones at similar ages as monolingual children (Bialytsok et al., 2009; Pearson, 2009). These milestones are similar to the ones mentioned earlier in L1 Acquisition, which include different aspects of language from “sound systems to grammar”.
The nuances though, is that bilingual children typically show comparable linguistic competence and performance in one language compared to monolingual peers, but not necessarily in both languages (Pearson, 2009). In fact, that is probably a function of the quantity and quality of language input received. In a certain sense, the linguistic knowledge of bilingual children is also distributed across languages (Bialytsok et al., 2009). No worries for parents to facilitate bilingualism in children, if there is guarantee of abundant and rich input in at least one of the languages.
4.3.2 Bilingual children are able to differentiate between their languages at a very young age.

Anecdotally, I have no lack of feedback from concerned parents on children getting confused with more than one language in early childhood, despite that fact that bilingualism in the environment is so much beyond their control. However, research has demonstrated that many bilingual newborns can already differentiate between languages (Sebastian-Galles, 2010; Sebastian-Galles & Santolin, 2020), even if they cannot produce words yet, although it may not necessarily be the target languages we are concerned with.
In fact, for more challenging languages which are rhythmically similar, bilingual children are also able to discriminate between the speech signals of both languages latest by 4-5 months. Such sensitivity to the linguistic cues and variations present in their linguistic environment continues to develop as these children grow and would gradually translate to other components of the language system.
4.3.3 An infant is considered bilingual only if it is exposed to either of the two languages in the range of 25%-75% of the time.
As a disclaimer, this is more of a professional agreement that is standardised for research than a strictly scientific criterion (though calibration has been factored in). This criterion of exposure to either language for at least 25% is an official one recognised by the ManyBabies Consortium (Sebastian-Galles & Santolin, 2020).
I do want to emphasise, though, that studies indicate that bilingual or multilingual children who receive at least 40%-60% exposure to a target language can achieve comparable language acquisition to monolingual peers, despite having less overall language input. Perhaps this can be assuring to parents among us on managing the linguistic environment at home to nurture bilingualism. If there is any rule of thumb, protect the space for the language that the family values which is not used widely in society (i.e. not a dominant societal language).
4.3.4 While bilingual children typically know fewer words in each language, their combined lexicon size surpasses that of monolinguals.

The 50-word landmark in lexicon size is generally achieved by both monolingual and bilingual children around 1.5 years of age. However, it is widely acknowledged that bilingual children typically possess a smaller lexicon in each of their target languages compared to their monolingual counterparts, primarily due to the reduced exposure and use of each language (Bialytsok et al., 2009; Sebastian-Galles & Santolin, 2020).
However, this difference diminishes as the children grow, since the rate of vocabulary growth decelerates with age (e.g. less words learned over time). Also, if we consider the total size of the bilingual lexicon, such as all the words combined in both languages (or more), bilingual children typically know more words than monolinguals. Again, this can be reassuring for parents among us who are bringing up bilingual children at home.
Conclusion: What are your beliefs about language development?
Till this point, I hope this starter’s guide has been helpful thus far. I do encourage us to continue reflecting on their notions regarding LANGUAGE ACQUISITION. By examining the complexities and nuances of L1, L2, L3 and Bilingual Language Acquisition, we can better review and re-shape our approaches in the different contexts.
Of course, a thorough exposition of the canonical insights from LANGUAGE ACQUISITION studies would warrant a comprehensive literature review article. For me, at least within this article, I shall bring out some interesting insights that I thought we could ponder over. They might be reductionist, as I hope not to overload this article. At least for LEA, I do plan to consolidate current progress in addressing the earlier mentioned research questions in future attempts with different languages as examples (including sign language). Do look forward to this and follow updates on this website!
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Recommended Readings
- Bialystok, E., Craik, F.I.M., Green, D.W., & Gollan, T.H. (2009). Bilingual minds. Psychological Science in the Public Interest, 10(3), 89-129.
- Clark, E. (2016). First Language Acquisition (Third Edition). Cambridge UK: Cambridge University Press.
- De Angelis, G. (2007). Third or Additional Language Acquisition. Bristol UK: Multilingual Matters.
- Gass, S.M., Behney, J., & Plonsky, L. (2020). Second Language Acquisition: An Introductory Course (5th Edition). New York USA: Routledge.
- Hammarberg, B., & Williams, S. (2009). A study of third language acquisition. In Hammarberg, B. (Ed.), Processes in Third Language Acquisition (pp. 17-27). Edinburgh: Edinburgh University Press.
- Hummel, K.M. (2014). Introducing Second Language Acquisition: Perspectives and Practices. Chichester UK: Wiley Blackwell.
- Lust, B. (2006). Child Language: Acquisition and Growth. New York USA: Cambridge University Press.
- Pearson, B.Z. (2009). Children with two languages. In Bavin, E.L. (Ed.), The Cambridge Handbook of Child Language (pp. 379-398). Cambridge UK: Cambridge University Press.
- Rowland, C. (2014). Understanding Child Language Acquisition. Abingdon UK: Routledge.
- Sadeghi, K. (2022). Talking About Second Language Acquisition. Cham Switzerland: Palgrave Macmillan.
- Saville-Troike, M., & Barto, K. (2017). Introducing Second Language Acquisition (Third Edition). Cambridge UK: Cambridge University Press.
- Saxton, M. (2017). Child Language: Acquisition and Development (Second Edition). London UK: SAGE Publications Ltd.
- Sebastian-Galles, N., & Santolin, C. (2020). Bilingual Acquisition: The Early Steps. Annual Review of Developmental Psychology, 2, 47-68.
References
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