Bilingualism and Brain Lateralization

Brain Lateralization and Neural Networks in Bilinguals
In recent years, various studies have been conducted on bilingualism in regard to the neural basis of the first language (L1) and second language (L2) processing. The new technical advances, such as position emission tomography (PET) and functional magnetic resonance imaging (fMRI) are used to determine whether L1 and L2 share a common neural network or whether languages are represented in different areas of the brain (Dehaene et al., 1997; Perani et al., 1998; Liu, Hu, and Peng, 2010). Studies in neuropsychology have shown that for most people language processing takes place in the perisylvian areas of the left hemisphere. Research on bilinguals and polyglots who suffered brain injury revealed that occasionally aphasia affects only one of the languages that were previously acquired. This finding suggests that languages are represented in different parts of the brain (Paradis, 1995, cited in Perani et al., 1998) and that L2 has reduced leftward lateralization (Albert & Obler, 1978, cited in Dehaene et al., 1997). Various studies that examined bilinguals and their language processing have shown that L2 in comparison to L1 doesn’t consistently activate the same neural networks across subjects. The inconsistency between participants could be attributed to the age of acquisition and proficiency level of L2 (Dehaene et al., 1997; Perani et al., 1998; Liu, Hu, and Peng, 2010). This paper examines whether L1 and L2 are supported by a common neural system or whether a dedicated cortical area represents each language. Furthermore, this paper identifies neural substrates activated by L1 and L2 during auditory, word production, and picture naming tasks.
Dehaene et al. (1997) examined bilinguals (French-English) who acquired L2 after the age of seven. The researchers found that while listening to a task the superior temporal sulcus (STS), superior and middle temporal guri (STG and MTG), temporal pole (TP), and left angular gyrus (AG) were constantly activated in the left hemisphere for L1. STS and TP were also activated in the right hemisphere but it varied across subjects and the activation wasn’t as strong as in the left hemisphere. In addition, the neural pathway didn’t extend to AG. The findings for L2 showed greater inter-subject variability than for L1. The results of fMRI found that six subjects activated STS, STG, and MTG in the left temporal lobe for L2. However, the pixels of these activations were dispersed compared to the results for L1. The second language didn’t cause any activation in the left TP and AG. Also, some of the subjects didn’t show any neural activation in the left temporal region, which suggests that L2 is mostly dominated by their right hemisphere. The results also displayed that subjects activated additional resources while listening to L2. These additional sub-regions were the right STG and STS in the right temporal lobe. In addition, results of L2 showed that some subjects activated various networks outside the temporal lobe. Specifically, these subjects used the left inferior frontal gyrus, located in the Broca’s area, the inferior precentral sulcus, and the anterior cingulate.

Get Help With Your Essay
If you need assistance with writing your essay, our professional essay writing service is here to help!
Essay Writing Service

The research shows that L1 consistently activated the temporal lobe, especially stimulating the STS, STG, and MTG in the left hemisphere. Some subjects also activated these cerebral regions for L2 but with greater dispersion. Participants had strong leftward lateralization for L1 and inconsistent lateralization patterns for L2 across subjects. These results are consistent with the hypothesis that L1 is represented in the left hemisphere for most people. Furthermore, the study suggests that late bilinguals require additional neural networks for L2. Therefore, some subjects recruited left inferior frontal gyrus, which is responsible for language production to help maintain L2 while processing it during tasks. The anterior cingulate was another additional resource, which is responsible for attention and control. This suggests that L2 is not as autonomic as L1 and subjects needed more resources and attention to process L2 (Pardo et al., 1990; Posner & Dehaene, 1994; Paulesu, Frith, & Frackowiak, 1993, cited in Dehaene et al., 1997).
Perani et al. (1998) studied cortical responses by evaluating bilinguals with high proficiency, late acquisition (HPLA) and high proficiency, early acquisitions (HPEA) and comparing their results with low proficiency, late acquisition (LPLA) study (Perani et al., 1996). Similar to previous studies, L1 of the LPLA bilinguals activated the left hemisphere, including perisylvian areas and temporal lobes and L2 activated different networks across subjects (Perani et al., 1996; Dehaene et al., 1997, cited in Perani et al., 1998). On the other hand, the results demonstrated that balanced bilinguals, HPLA and HPEA, activated similar networks while listening to stories in their native and acquired languages. HPLA subjects activated left hemisphere in the temporal pole, the STS, MTG and hippocampal structures for L1, which is consistent with previous results. However, L2 activated similar neural pathways, which suggests that when L2 is acquired to a high proficiency the speakers activate the same areas of the brain for both languages. HPEA subjects activated temporal poles, hippocampal structures and lingual gyrus for both, L1 and L2, which is similar to the results of HPLA speakers. These results show that once the proficiency level of L2 increase, the speakers recruit less networks to maintain L2 and the activation foci between languages doesn’t vary as it does with unbalanced bilinguals (e.g., LPLA). Furthermore, the results showed that the temporal lobes were consistently activated during tasks. Previous studies showed that the temporal poles get activated during tasks that require listening, reading, or speaking (Mazoyer et al., 1993; Perani et al., 1996, cited in Perani et al., 1998). Therefore, the authors suggest that the temporal poles are responsible for processing at the sentence level rather than unconnected word level.
In another study, Liu, Hu, and Peng (2010) examined Chinese-English bilinguals using word production and picture naming tasks. The results showed that there was increased activation for L2 in the left inferior frontal gyrus (IFG), bilateral supplementary motor area (SMA), left precentral gyrus, Brodman’s area (BA) and bilateral basal ganglia, including the putamen, globys pallidus, and caudate, and bilateral cerebella.The bilateral SMA, left precentral gurys, and the cerebella functions are related to motor processing for word production; therefore, activation in these regions might be related to phonological and articulatory processing in language production. The researchers also found that L2 activated Brodman’s area of BA44/45/48; the BA44 and BA 45 are known are Broca’s area, which is responsible for motor planning and articulation, as well as phonological processing. Activations in these areas suggest that L2 is less autonomic and requires more neural pathways to maintain and control language production for L2 (Braun et al., 2001, cited in Liu, Hu, and Peng, 2010). L2 also activated regions of basal ganglia, which is related to motor behavior and cognition functions (Graybiel, 2000) and regulates planning and execution of actions, and speech motor control. The activations in these areas could be attributed to the fact that unbalanced bilinguals try to reduce interference from a more dominant L1 (Elsinger et al., 2006; Alm, 2004, cited in Liu, Hu, and Peng, 2010). Interestingly, the authors found that L1 activated the right putamen and right globus pallidus of the right basal ganglia. The dissociation between L1 and L2, which activated the left basal ganglia, suggests that different regions of basal ganglia are responsible for different levels of speech execution( Jueptner and Weiller, 1998, cited in the study). The difference between activation of basal ganglia could also be attributed to the fact that Chinese and English use different phonological systems and language scripts, which might activate different parts of basal ganglia (Liu et al., 2006, cited in Liu, Hu, and Peng, 2010). The results also showed overlapping between neural pathways for L1 and L2. Both languages activated the left IFG, which is associated with semantics and phonology, posterior perisylvian area which is responsible for linguistic functions and the cingulate gyrus for cognition and motor control.
The literature review and the present studies concur that L1 has a consistent neural pathway within the left hemisphere and L2 has a more varied cerebral activation patterns. The differences between L1 and L2 are being attributed to the language proficiency of L2 Dehaene et al., 1997; Perani et al., 1998; Liu, Hu, and Peng, 2010). Nonetheless, L1 and L2 also activate common neural system, which differed from one study to another due to the tasks, languages involved, and the level of L2 acquisition. The results of the studies suggest that L2 is less autonomic than L1 and requires more resources to maintain the L2, however as the proficiency of L2 increases the need to activate varied neural pathways decreases, as L2 becomes competent to L1. It’s important to study about the way languages are represented in peoples’ brain as these studies will contribute to our understanding of brain plasticity, language acquisition and neurological diseases, such as aphasia in bilinguals. Also, new studies using advanced technologies will help to clarify agreed upon hypothesis of language lateralization and representation in the human brain.
Dehaene, S., Dupoux E., Mehler, J., Cohen, L., Paulesu, E., Perani, D., et al. (1997). Anatomical variability in the cortical representation of first and second language. Neuroreport, 8, 3809–15.
Liu, H., Hu, Z., Guo, T., Peng, D. (2010). Speaking words in two languages with one brain: neural overlap and dissociation. Brain Research, 1316, 75-82.
Perani, D., Paulesu, E., Galles, N.S., Dupoux E, Dehaene S, Bettinardi V, et al.(1998). The bilingual brain: proficiency and age of acquisition of the second language. Brain, 121, 1841–52.

Effects of Bilingualism on the Acquisition of a Third Language

An analysis of the effects of bilingualism on the acquisition of a third language.

Literature review

The study of third language acquisition combines two fields which have in previous years remained separated by researchers: second language acquisition and bilingualism.

Cenoz (2003, p.71) describes third language acquisition as the “ability to acquire a non-native language by learners who have previously acquired or are acquiring two other languages.” It is also mentioned that the acquisition of the first two languages can either be simultaneous or consecutive.

 “Generative studies on L3 acquisition only began to surface in significant numbers in the latter part of the 2000s (e.g. Leung, 2001, 2005, 2007a, 2007b; Flynn et al., 2004; Bardel and Falk, 2007; Jaensch, 2008; Cabrelli Amaro et al., 2009; Cabrelli Amaro and Rothman, 2010).” (Rothman, J., Iverson, M. & Judy, T. 2011). In the field it is generally acknowledged that Pearl and Lambert’s study (1962) on the effect of bilingualism on cognitive development was a significant breakthrough in the study of bilingualism (Baker, 2001; Hamers & Blanc, 2000).

Get Help With Your Essay
If you need assistance with writing your essay, our professional essay writing service is here to help!
Essay Writing Service

In the Sixties and Seventies researchers such as Albert & Obler, 1978; Jacobsen & Imhoof, 1974; Lerea & Kohut, 1961; Saif & Sheldon, 1969; Vildomec, 1963 proposed that additional languages are acquired by bilinguals and multilinguals more efficiently than by monolinguals. This means that the more languages a person knows, the easier it is for them to acquire additional languages. If this is the case, bilinguals will make more significant progress when learning a third language than a monolingual would when learning a second language.

This can be supported by the study carried out by McLaughlin, B., & Nayak, N. (1989) which compared the strategies used by monolingual and bi/multilingual learners, reporting that bilinguals and multilinguals use a fuller range of linguistic and mnemonic strategies thus being more flexible in their use than monolinguals. This is due to third-language students having the ability to use their knowledge of two languages and the experience of the acquisition process of another language, compared to second language students who can only use their first.

Lado (1957) created the Contrastive Analysis Hypothesis (CAH) which claims that when learning a new language it is possible to predict learning difficulties and identify patterns (Ellis, 1986). Lado (1957) made the assumption that “…the student who comes into contact with a foreign language will find some features of it quite easy and others extremely difficult. Those elements that are very similar to his native language will be simple for him, and those elements that are different will be difficult” (Lado, 1957, p. 2 in Ellis 1994, p.306 cited by Tao, Guo et al (2008)).

This study can be supported by the behaviourist theory (Ellis, 1986) which suggests that ‘old habits get in the way of learning new habits’; this refers to the interferences from L1 over L2, resulting in proactive inhibition. This proactive inhibition implies that transfer will be negative when L1 and L2 share a meaning but express it in a different way, for example a native Italian speaker wanting to express their age through the phrase ‘I have 24 years’ in L2 English. For a bilingual who has the ability to draw on an already similar L2, for example another latinate language, it may be possible to avoid this interference.

Rothman, et al. (2011) believes that there are at least four logical possibilities for how transfer manifests, since L3 has more than one possible source of transfer.

1 – “No transfer position” (Rothman, et al. 2011. p.8). This suggests that the initial state of any adult language learning situation is one and the same, devoid of previous linguistic knowledge at the level of morphosyntactic structure. Though this position has never been defensibly claimed in L3 research, it could be argued and tested on the basis of extending the no transfer hypothesis from L2 into L3 studies (e.g. Epstein et al., 1996; Platzack, 1996).

2 – ‘’L1 factor” (Rothman, et al. 2011. p.8). This position gives the privileged status as the sole source of morphosyntactic transfer to all cases of language acquisition in adulthood to the L1, possibly for process ability reasons (Håkansson et al., 2002). This factor is based on cases of L3 acquisition after adult L2 acquisition as opposed to adult L3 acquisition after child L2 or simultaneous bilingualism; as the L2 features are new and they should not be available for transfer.

3 – ‘L2 status factor’ formalised by Bardel and Falk (2007 and 2011) while borrowing the label from work on the L3 lexicon by Williams and Hammarberg (1998) and Hammarberg (2001) suggests that L2 has a privileged standing for morphosyntactic transfer. Bardel and Falk (2007) concluded that the most recently acquired language, L2, precluded direct access to the morphosyntactic L1 system, even when there were linguistic relations and related relationships between L1 and L3.

4 – The fourth position rejects the notion of a privileged transfer status for either of the two previously acquired systems, thus maintaining that features and functional categories from either the L1 or L2 can be transferred. Such an approach has been divided under two formal models, the Cumulative Enhancement Model (C.E.M.) of Flynn et al. (2004) and the Typological Primary Model (T.P.M.) of Rothman (2011). These two models are remarkably different from each other although it is agreed that all previously acquired language characteristics are available for transfer.

C.E.M. was based on the investigation of L3 oral production of restrictive relative clauses in L1 Kazakh / L2 Russian / L3 English speakers made by Flynn et al. (2004). Based on C.E.M., language acquisition is both cumulative and non-redundant, signifying that any prior language can either facilitate subsequent language acquisition or remain neutral. C.E.M. also predicts that if transfer is negative between one of the sources and the L3, then transfer simply does not obtain, and any previously acquired linguistic knowledge from both L1 and L2 can only positively impact the acquisition of L3.

T.P.M. (Rothman et al., 2011)  theorises that non-facilitative transfer can occur based on typological proximity – actual or real – between the languages. Though T.P.M. is formalised in Rothman’s article (2011), it stems from his previous collaborative work with Cabrelli Amaro, (2010) in which they investigated L3 French and Italian, where English was the L1 and successful Spanish was the L2. Throughout their research they examined properties related to the Null-Subjects Parameter (a sentence in which the subject is absent). It was demonstrated that the L3 learners transferred Spanish, the L2 and typologically related language, even though English is able to provide a correct value for French.

Rothman et al (2011) showed that the C.E.M.’s expectations that negative transfer does not occur was not verifiable. In view of their methodology, they were unable to distinguish a true typological primacy approach from an L2 status factor as the two variables overlapped. Though, work that is able to differentiate these variables, e.g. evidence presented in Rothman et al. (2011) and Montrul et al.’s (2011) studies, outwardly favour a strong role for typological proximity as a deterministic variable. This is perhaps the most significant variable when deciding between what factors form multilingual transfer.

Generative L3 acquisition has inherited a number of key questions from L2 acquisition, including the issue of full transfer, partial transfer & no transfer at the initial case of acquisition. Unlike L2 acquisition, L3 acquisition occurs in the presence of not just one, but two potential sources of Cross Linguistic Influence (CLI) on a subsequently acquired language. The key issue in this regard is whether the two previously learned languages have an affect on L3 acquisition, or whether it is only one of the languages that is the main or only source of CLI. (Westergaard et al. 2017. p.667).

Find Out How Can Help You!
Our academic experts are ready and waiting to assist with any writing project you may have. From simple essay plans, through to full dissertations, you can guarantee we have a service perfectly matched to your needs.
View our services

In the case of CLI coming from the previous two languages learnt, it is usually assumed that the source of influence is determined on a property-by-property basis (e.g. Berkes & Flynn, 2012; Flynn et al., 2004). However, in the case of only one language being the main source, transfer may be assumed to happen all at once (e.g. Leung, 1998, 2003; Rothman, 2011, 2015).

A variety of factors have been said to affect the choice of language for CLI, including order of acquisition (e.g. Bardel & Falk, 2007; Jin, 2009; Na Ranong & Leung, 2009) and typological proximity, as supported by Rothman et al. (2011).  This is also supported by studies carried out by De Angelis, 2007; Foote, 2009; Leung, 1998, 2003; Rothman & Cabrelli Amaro, 2010.

Order of acquisition. One of the possible scenarios in L3 acquisition is transfer from the L1, this indicates that the learner’s native language is the main source of influence.

Other studies have found influence from the L2, this led to the L2 Status Factor model, according to which the L2 is a privileged source of transfer, especially at early stages (Bardel & Falk, 2007, 2012). The L2 Status Factor model has supporting experimental evidence that suggests that implicit linguistic competence and explicit metalinguistic knowledge are neuro linguistically distinct and have different memory sources (Paradis, 2004, 2009), the former being sustained by procedural memory and the latter by declarative memory (Ullmann, 2001). This means that while L1 grammar is implicitly acquired and sustained by procedural memory, L2 grammar is usually based on precise knowledge and sustained by declarative memory. Therefore, since L3 grammar is learned the same way as L2 grammar, transfer will occur between the two languages that are both stored in declarative memory (Westergaard et al. 2017).

Typological Proximity. Westergaard et al. (2017) discusses some models of L3 acquisition, including those that argue that either the L1 or the L2 has a privileged status with respect to CLI. It then goes on to consider models that focus on the role of structural factors, including The Cumulative Enhancement Model (C.E.M.) (Berkes & Flynn, 2012; Flynn et al., 2004) as well as typology-based models such as The Interlanguage Transfer Hypothesis (I.T.H.) (Leung, 1998, 2003), the Typological Primacy Model (T.P.M.) (Rothman, 2011, 2015) and The Linguistic Proximity Model (Westergaard et al. 2017).

The Interlanguage Transfer Hypothesis. I.T.H. uses Kellerman’s (1979, 1983) idea of psychotypology, signifying the use of the language learner’s perception of the source and target languages’ properties as close vs. distant and core vs. non-core. Following this theory it would be predicted to see  transfer affecting close/core properties. Referring to the Full Transfer Full Access hypothesis (Schwartz & Sprouse, 1996), Leung proposed that full transfer would be seen during L3 acquisition from the most psycho-typologically close language. The I.T.H. thus argues that ‘the Ln initial state is the steady state of a previously acquired (inter)language which is typologically closest to Ln’ (Leung 2003, p.199).


The Linguistic Proximity Model. The most significant counter for typology-based models is the reported existence of CLI from the typologically more distant language, e.g. Jin (2009) showed the influence from L1 Chinese (instead of L2 English) into L3 Norwegian, and Hermas (2014), showed the influence from L1 Arabic (instead of L2 French) into L3 English. The C.E.M., contrarily, cannot explain the findings of non-facilitative influence in L3 acquisition, e.g. Rothman and Cabrelli Amaro (2010), shows transfer from L2 Spanish into L3 French for the null subject property. The L.P.M., in turn, argues that CLI happens from both previously learned languages.

The L.P.M. builds on what is considered to be the positive aspects of the C.E.M. and the T.P.M., in the sense that certain similarities between the three languages play a major role, not just the order of acquisition. Instead of arguing that general typological proximity is the decisive factor, Westergaard et al. (2017) claims that similarity of abstract linguistic properties is the main cause of CLI from previously learned languages; L.P.M. therefore allows for both facilitative and non-facilitative influence.

Other studies on bilinguals (e.g. Bialystok, 2011) show that the language that is not in use still remains active and must typically be inhibited when speaking the other language.

This means that bilinguals learning an L3 (whether they have two first languages or an L1 plus an L2) should be able to benefit from both of the languages they know. Conversely, they may also experience some non-facilitative influence from either language. (Westergaard et al. 2017).

Additionally, the L.P.M. predicts different learning patterns for different linguistic phenomena. Westergaard et al. (2017) explains that the source of CLI with respect to a particular property is based on structural similarities between the L3 and one or both of the previously acquired languages, rather than overall typological proximity between just one of them and the L3. Evidently, this kind of CLI could take place only if the learner is able to identify abstract linguistic properties.

Unlike any typology-based models, the L.P.M. does not assume the idea of complete transfer of one of the previously acquired grammars early on in L3 acquisition, and excludes any influence from the other language at this stage. (Westergaard et al. 2017).

The majority of research identifies the typological proximity between L1/L2 and L3 to be the main cause of interference of L3 acquisition. It could therefore be argued that bilinguals have a stronger chance of interference due to the two language bases already known, as a learner could see interference from just one or both of these languages. On the other hand, there is evidence for positive transfer because of the two languages as seen in the behaviourist theory (Ellis, 1986). There is however very little research done in this field so far and so further investigations would be needed to form a concrete answer on how bilingualism affects L3 acquisition.


Albert, M. L., & Obler, L. K. (1978). The bilingual brain. New York: Academic Press.

Baker, C. (2001). Foundations of bilingual education and bilingualism. Clevedon: Multilingual Matters.

Bardel, C. and Falk, Y. (2007).The role of the second language in third language acquisition: The case of Germanic syntax. Second Language Research 23: 459–84.

Bardel, C., & Falk, Y. (2012). Behind the L2 Status Factor: A neurolinguistic framework for L3 research. In J. Cabrelli Amaro, & J. Rothman (Eds.), Third language acquisition in adulthood (pp. 61–78). Amsterdam, Holland: John Benjamins.

Berkes, É., & Flynn, S. (2012). Further evidence in support of the Cumulative-Enhancement Model: CP structure development. In J. Cabrelli Amaro, & J. Rothman (Eds.) Third language acquisition in adulthood (pp. 143–164). Amsterdam, Holland: John Benjamins.

Bialystok, E. (2001). Bilingualism in development. Cambridge, U.K.: Cambridge University Press.

Bialystok, E. (2011). Reshaping the mind: the benefits of bilingualism. Canadian Journal of Experimental Psychology, 65, 229–235.

Cenoz, J. (2003). The additive effect of bilingualism on third language acquisition: A review. International Journal of Bilingualism, 7(1), 71–87. 

Cenoz, J., & Hoffmann, C. (2003).Acquiring a third language: What role does bilingualism play? International Journal of Bilingualism, 7(1), 1–5. 

De Angelis, G. (2007). Third or additional language acquisition. Clevedon, UK: Multilingual Matters.

Ellis, Rod (1986). Understanding Second Language Acquisition. Oxford, Oxford University Press.

Epstein, S., Flynn, S. & Martohardjono, G. (1996). Second language acquisition: Theoretical and experimental issues in contemporary research. Behavioural and Brain Sciences 19: 677-714.

Flynn, S., Foley, C., and Vinnitskaya, I. (2004). The cumulative-enhancement model for language acquisition: Comparing adults’ and children’s patterns of development in first, second and third language acquisition of relative clauses. The International Journal of Multilingualism 1: 3–16.

Foote, R. (2009). Transfer in L3 acquisition: The role of typology. In Y-K. I. Leung (Ed.), Third language acquisition and universal grammar (pp. 89–114). Clevedon, UK: Multilingual Matters.

Hamers, J., & Blanc, M. (2000). Bilinguality and bilingualism. Cambridge, U.K.: Cambridge University Press.

Hammarberg, B. (2001).Roles of L1 and L2 in L3 production and acquisition. In: Cenoz, J., Hufeisen, B., and Jessner, U. (eds) Cross-linguistic influence in third language acquisition: Psycholinguistic perspectives. Clevedon: Multilingual Matters, 21–41.

Håkansson, G., Pienemann, M., and Sayheli, S. (2002).Transfer and typological proximity in the context of second language processing. Second Language Research 18: 250–73.

Hermas, A. (2014). Multilingual transfer: L1 morphosyntax in L3 English. International Journal of Language Studies, 8(2), 10–24.

Jacobsen, M., & Imhoof, M. (1974).Predicting the success in learning a second language. Modern Language Journal, 58, 329 – 336.

Jin, F. (2009). Third language acquisition of Norwegian objects: Interlanguage transfer or L1 influence? In Y-k. I. Leung (Ed.), Third language acquisition and universal grammar (pp. 144–161). Bristol, UK: Multilingual Matters.

Kellerman, E. (1983). Now you see it, now you don’t. In Gass, S. & Selinker, L. (Ed.), Language Transfer in Language Learning, pp. 112-134. Rowley, MA: Newbury House.

Lado, R. (1957) Linguistics across Cultures: Applied Linguistics and Language Teachers. University of Michigan Press, Ann Arbor.

Lerea, L., & Kohut, S. (1961).A comparative study of monolinguals and bilinguals in a Verbal Task Performance. Journal of Clinical Psychology, 17, 49–52.

Leung, Y.-k. I. (1998). Transfer between interlanguages. Proceedings of the 22nd Boston University Conference on Language Development, pp. 477–487. Somerville, MA: Cascadilla Press.

Leung (2003). Failed features versus full transfer full access in the acquisition of a third language: Evidence from tense and agreement. Proceedings of the 6th Generative Approaches to a Second Language Acquisition Conference (GASLA 2002), pp. 199–207.

Lozano, C. (2003). Focus, pronouns and word order in the acquisition of L2 and L3 Spanish. Unpublished doctoral dissertation, University of Essex, UK.

Montrul, S., Dias, R., and Santos, H. (2011).Clitics and object expression in the L3 acquisition of Brazilian Portuguese: Structural similarity matters for transfer. Second Language Research 27: 21–58.

Na Ranong, S., & Leung, Y-k. I. (2009). Null objects in L1 Thai-L2 English-L3 Chinese: An empirical take on a theoretical problem. In Y-k. I. Leung (Ed.), Third language acquisition and universal grammar (pp. 162–191). Bristol, UK: Multilingual Matters.

Paradis, M. (2004). A neurolinguistic theory of bilingualism. Amsterdam, Holland: John Benjamins.

Paradis, M. (2009). Declarative and procedural determinants of second languages. Amsterdam, Holland: John Benjamins.

Pearl, E., & Lambert, W. E. (1962).The relationship of bilingualism to intelligence. Psychological Monographs, 76, 1–23.

Platzack, C. (1996).The initial hypothesis of syntax: A minimalist perspective on language acquisition and attrition. In: Clahsen, H. (ed.) Generative perspectives on language acquisition. Amsterdam: John Benjamins, 369–414.

Rothman, J., Iverson, M., & Judy, T. (2011).Introduction: Some notes on the generative study of L3 acquisition. Second Language Research, 27(1), 5-19.

Rothman, J. (2011).L3 syntactic transfer selectivity and typological determinacy: The typological primacy model. Second Language Research, 27: 107–27.

Rothman, J., & Cabrelli Amaro, J. (2010). What variables condition syntactic transfer? A look at the L3 initial stage. Second Language Research, 23, 189–218.

Rothman, J. (2015). Linguistic and cognitive motivations for the typological primacy model (TPM) of third language (L3) transfer: Timing of acquisition and proficiency considered. Bilingualism: Language and Cognition, 18(2), 179–190.

Saif, P. S., & Sheldon, M. E. (1969). An investigation of the experimental French Program at Bedford Park and Allenby Public Schools. Toronto: Toronto Board of Education.

Schwartz, B. D., & Sprouse, R. A. (1996). L2 cognitive states and the full transfer/full access model. Second language research, 12(1), 40-72.

Tao, G, Lijuan, Z and Gann, R.R (2008). Studies on Contrastive Analysis. International Forum of Teaching and Studies, 4 (1), pp. 62-74,118-119.

Ullman, M. (2001). The neural basis of lexicon and grammar in first and second language: The declarative/ procedural model. Bilingualism: Language and Cognition, 4(2), 105–122.

Vildomec, V. (1963). Multilingualism. Berlin: Sythoff-Leyden.

Westergaard, M. (2009). The acquisition of word order: Micro-cues, information structure and economy. [Linguistik Aktuell/Linguistics Today 145]. Amsterdam: John Benjamins.

Westergaard, M. (2014). Linguistic variation and micro-cues in first language acquisition. Linguistic Variation, 14(1), 26–45.

Westergaard, M., Mitrofanova, N., Mykhaylyk, R., & Rodina, Y. (2017). Crosslinguistic influence in the acquisition of a third language: The Linguistic Proximity Model. International Journal of Bilingualism, 21(6), 666–682. 

Williams, S. and Hammarberg, B. (1998).Language switches in L3 production: Implications for a polyglot speaking model. Applied Linguistics, 19: 295–333.