A Journal of Culture, English Language, Teaching & Literature ISSN 1414-3320 (Print), ISSN 2502-4914 (Online) Vol. 22 No.1; June 2022 Copyright © Soegijapranata Catholic University, Indonesia Unpacking the Layers: Understanding The Multifaceted Nature of L2 Learning Complexity 1Muhammad Fahruddin Aziz, 2Herlandri Eka Jayaputri 1Sekolah Tinggi Ilmu Hukum Biak-Papua 2Akademi Perikanan Kamasan Biak-Papua 1azizfahruddin@gmail.com, 2herlandrieka@gmail.com Received: 07-03-2022 Accepted: 11-05-2022 Published: 30-06-2022 https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ Unpacking the Layers: Understanding The Multifaceted Nature of L2 Learning Complexity 1Muhammad Fahruddin Aziz, 2Herlandri Eka Jayaputri 1azizfahruddin@gmail.com, 2herlandrieka@gmail.com 1Sekolah Tinggi Ilmu Hukum Biak-Papua 2Akademi Perikanan Kamasan Biak-Papua Abstract: The impact of age on language learning is often explained by various factors such as neural mechanisms, biological influences, and learning conditions. This study is a literature review that aims to analyze age influences based on various sources, including journals, books, and proceedings. The study argues that there is a cognitive mechanism known as the language defense mechanism that acts as a barrier to maintain the integrity of L1 information, leading to challenges in acquiring L2 for adults. This defense mechanism strengthens as L1 knowledge increases, making it more difficult to learn L2. The concept of the defense mechanism provides another perspective on models such as fossilization, language interference, the impact of age, and bilingualism in the context of learning new languages. Key words: language interference, age effect, language defense mechanism Abstrak: Pengaruh usia pada pembelajaran bahasa sering dijelaskan dengan berbagai faktor seperti perbadaan mekanisme otak, pengaruh biologis, dan perbedaan kondisi pembelajaran. Studi ini merupakan sebuah tinjauan literatur yang bertujuan untuk menganalisis pengaruh usia berdasarkan berbagai sumber, termasuk jurnal, buku, dan prosiding. Studi ini menjeleaskan bahwa terdapat mekanisme kognitif yang disebut sebagai mekanisme pertahanan bahasa yang bertindak sebagai penghalang untuk menjaga agar informasi L1 tetap utuh, yang kemudian menyebabkan kesulitan dalam memperoleh L2 pada orang dewasa. Mekanisme pertahanan ini semakin menguat seiring berkembangnya pengetahuan L1. Konsep mekanisme pertahanan ini memberikan perspektif lainnya selain konsep-konsep seperti fosilisasi, 96 Celt: A Journal of Culture, English Language Teaching & Literature, Volume 22, Number 1, June 2022, pp. 96 – 113 https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ interferensi bahasa, pengaruh usia pembelajaran, dan bilingualisme dalam konteks pembelajaran bahasa baru. Kata kunci: language interference, age effect, language defense mechanism. INTRODUCTION In Indonesia, it has been observed that Language Learners tend to deviate from the standard English norms when using certain words or phrases (Arifin, 2016; Ginting, 2019; Septina Sulistyaningrum, 2020). For example, instead of using the suffix “-ren” to indicate plural form, their brains are inherently wired to utilize the reduplication pattern of “child-child” as a linguistic norm. Similarly, when indicating possession, they use an inverted word order like “bag Andy” instead of the correct word order “Andy's bag” It is important to note that these language learners are consistent in their usage of these constructions, and we have paid careful attention to their usage. However, it is also true that these constructions do not correspond to the rules of standard English. It appears that these learners have deviated from the English norm in order to adjust to the rules of English when attempting to correct their constructions. This observation raises questions about the nature of language learning and how learners adapt to new languages. It is possible that the learners are unconsciously applying their native language rules to English, resulting in these deviations. Further research and analysis are required to better understand these phenomena and to develop effective language learning strategies that can help learners avoid such deviations. When Indonesian language learners attempt to adhere to the standard linguistic system of English, deviant constructions may arise. It is worth noting that linguistic variation is an inherent characteristic of language and occurs systematically. According to Mendívil-Giró (2019) research, language is arbitrary due to the lack of a natural association between language forms and referents. Indonesian learners’ use of English may exhibit changes in the standard English linguistic system due to the influence of their L1 construction. It is intriguing to consider the systematic manner in which they produce these incorrect constructions. This phenomenon raises questions about the mechanisms at play in the minds of these learners that consistently prompt them to create deviant constructions. If there is indeed a mechanism driving Aziz, M.F., Jayaputri, H.E., Unpacking the Layers: Understanding The 97 Multifaceted Nature of L2 Learning Complexity https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ these deviant constructions, it brings up further questions about how it affects the retention of the linguistic system in the minds of these learners. This highlights the importance of further research to gain a deeper understanding of the language learning process and how learners adapt to new linguistic systems. Such research could potentially lead to more effective language learning strategies that take into account the innate mechanisms at play in the minds of language learners. METHOD The research methodology employed in this study is library research. Its primary objective is to conduct a theoretical analysis of the age-related influences on learning. These influences include competition between different learning mechanisms, biological factors, and the conditions necessary for learning individual differences. To achieve this goal, various references from reputable sources such as journals, books, and proceedings are utilized. The documentation technique is employed to collect relevant information from these literatures. The central focus of this research is comprehensively understood through the application of qualitative data analysis. The objective of this analysis is to uncover the underlying essence of the research topic and develop a nuanced understanding of the complex relationships between the various age-related influences on learning. This research methodology offers a strong foundation for thoroughly investigating the fundamental elements that influence the learning process in various age cohorts. Employing various data sources and a thorough qualitative analysis guarantees the credibility and dependability of the outcomes of this research study. In the end, this research has the possibility to influence education policies and methodologies, and assist in developing more efficient learning approaches that cater to the specific requirements of various learners. RESULTS AND DISCUSSIONS A. Language Learning and Change: Impact and Factors The impact of the Indonesian language system on language learners is profound. The system is so ingrained in their mental representations that they 98 Celt: A Journal of Culture, English Language Teaching & Literature, Volume 22, Number 1, June 2022, pp. 96 – 113 https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ apply it even when using standardized English, resulting in deviations from standard English in areas such as reduplication, plurality, and possession. This phenomenon can be explained by the usage-based theory of language learning, which suggests that understanding the structure of language is acquired through real-world experiences of using language, rather than the learning of grammatical rules alone (Ghalebi & Sadighi, 2015; Koster, 2015). This indicates that language learning is a dynamic process that involves more than just memorizing rules. Language learners must also have practical experience using the language in real-life contexts to fully understand its nuances and intricacies. Through this approach, it is possible for individuals to gain a more comprehensive comprehension of the language system and acquire a high level of proficiency in its usage. Additionally, the mental representations of language systems are influenced by the context in which they are used. As language learners are exposed to different languages and language systems, their mental representations adapt and evolve to reflect their experiences. The significance of context and practical application in language learning, as well as the adaptable nature of mental representations of language systems, are underscored by these findings. Language learners from Indonesia are profoundly influenced by their native language system. The usage-based theory of language acquisition prioritizes hands-on experience and contextual immersion in language learning, while also emphasizing the dynamic and ever- evolving nature of mental representations of language systems. According to (Koster, 2015), both adults and children have a natural tendency to observe the patterns of their daily language use. When two constituents frequently occur together, attention is drawn to the regularity of the pattern, which helps to promote the formation of grammatical mental representations. This finding may explain why the standardized language system in our hometown has undergone changes, as the local language learners have internalized the patterns of their first language and applied them to their use of standardized English. Furthermore, the development of grammatical cognitive representations is not a static process but rather a dynamic one that can be impacted by changes in language usage. As language undergoes transformation and changes over time, mental representations of its grammar can also evolve accordingly. This highlights the importance of ongoing exposure to and use of a language, as it allows language learners to adapt to changes in the language and continue developing their understanding of its grammar. The study highlights the importance of daily language usage in the process of language acquisition. By Aziz, M.F., Jayaputri, H.E., Unpacking the Layers: Understanding The 99 Multifaceted Nature of L2 Learning Complexity https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ observing and internalizing the language usage patterns, language learners can create cognitive representations that assist them in acquiring grammatical knowledge of the language. The research also emphasizes the significance of maintaining a flexible approach towards language learning and continually adapting to changes in the language over time. The construction of interrogative sentences in English involved subject and verb inversion before the 1700s, but after this time, the auxiliary was incorporated into negative and interrogative constructions, according to Kroch (1989). While this change may seem uncertain and even unusual to some, Keller (1994, p.7) argues that language change does not occur due to changes in external conditions. Rather, despite changes in language, it remains a systematic entity. This prompts inquiries about the factors that uphold the coherence of the language system within the neural framework, even when language change is possible. Who decides which language inputs and outputs are acceptable, and what methods are used to determine the appropriate language use approach? These are important considerations that arise when examining the relationship between language change and linguistic structure. By exploring these issues, we can gain a deeper understanding of how language evolves over time and what factors contribute to its ongoing development. There are various suggestions that attempt to explain the causes of language change. One such proposition is that children are responsible for generating language change, as argued by scholars like Bohn et al. (2019 and Denman et al. (2017). According to this view, children adopt and reconceptualize linguistic input in a way that contrasts with the grammar of adults, leading to language changes. However, it should be noted that most changes in a child’s language system are temporary because of their eventual development of an adult-like language system. Therefore, the changes derived from the use of children’s language may be considered doubtful. Another proposition is that language change may come from the use of adult language, as it is adults who create available linguistic regularity (Denman et al., 2017). Moreover, social factors, such as social behavior, may also play a role in causing language changes (Nevalainen & Raumolin-Brunberg, 2017). Given the various ideas put forth, there is no definitive explanation regarding the causes of language change. However, it is crucial to note that any new language system that emerges through language change should remain a systematic entity, with questions arising as to what maintains the integrity of the language system in the neural system despite the occurrence of language changes. 100 Celt: A Journal of Culture, English Language Teaching & Literature, Volume 22, Number 1, June 2022, pp. 96 – 113 https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ In this particular study, the researchers have taken a keen interest in exploring the notion of language change that may be brought about by adults. While it is well established that changes in language are quite common and can often be observed occurring in a single generation, particularly with regard to alterations in vocabulary (as noted by Mair in 2015), it is imperative to consider the role that maturational constraints may play in any language changes that are instigated by adults. In other words, it is important to investigate whether the changes that occur in the language system as a result of adult influence are limited by the cognitive and neurological development of the individuals involved. By considering this factor, the researchers aim to gain a more comprehensive understanding of the potential for language change that exists within a given linguistic community. B. The Impact of Age on Language Acquisition The acquisition of language is affected by various factors, with maturity being a crucial aspect. It is widely accepted that different individuals have different achievements in language acquisition. However, maturational constraints indicate that there is a specific period during which language can be acquired with ease. According to Long (2013, p.4), individuals are more sensitive to language input during this period, which facilitates significant learning abilities. Despite a wealth of research on the critical period for language acquisition, SLA scholars have not yet arrived at a definitive conclusion. However, studies have indicated that immigrant refugee children acquire a second language more rapidly than their parents. This is due to the heightened sensitivity of individuals between the ages of 0 and 6 years, who are capable of attaining language abilities comparable to those of native speakers. Conversely, individuals aged between 12 and 17 years are less likely to achieve the same level of fluency as native speakers (Long, 2013, p.5-6). Newport's (2018) conducted a study to explore the impact of age of acquisition on second language acquisition. The research evaluated the language proficiency of participants in English grammar, comprising both grammatically correct and incorrect sentences. The study's results indicated that individuals who acquired English at a younger age attained higher scores in the proficiency test. On the other hand, individuals who started their English language learning at 15 years old or above faced challenges in achieving native-like proficiency and showed more diverse test scores. These findings imply that the age at which one starts acquiring a language plays a Aziz, M.F., Jayaputri, H.E., Unpacking the Layers: Understanding The 101 Multifaceted Nature of L2 Learning Complexity https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ vital role in language learning, and it is comparatively easier to learn a second language at a younger age. Additionally, it suggests that the later a person initiates language learning, the more challenging it becomes to achieve the same level of proficiency as a native speaker. Studies conducted in the area of second language acquisition have investigated the relationship between the age of second language learning and the ability to acquire a second language. Schmid (2014) carried out research aimed at examining how age influences non-native English speakers in acquiring a second language. The findings of the study revealed that the participants’ native language backgrounds had a more profound effect on their second language acquisition than their age. Interestingly, the language abilities of participants who acquired the second language beyond the critical period were found to be better, which is surprising. Bialystok & Miller (1999) conducted a study that compared the English language proficiency of three different groups of participants: native Chinese speakers, native Spanish speakers, and native English speakers. The findings of this study indicated that native Spanish speakers outperformed native Chinese speakers in terms of English proficiency. Bialystok & Miller's study in (1999) found that the effect of age did not have a significant impact on native Chinese speakers' ability to acquire a second language. The researchers emphasized that the differences in scores between the participants were closely related to the differences in linguistic structure or the way the measurement was given, rather than the age of acquisition (critical period). These research studies indicate that the correlation between the age of acquisition and the acquisition of a second language is not simple and can be influenced by multiple factors, such as one's mother tongue and the method of measuring language proficiency. However, these findings do confirm the concept of a critical period for language acquisition, beyond which acquiring native-like proficiency in a second language becomes more challenging. Lightbown & Spada (2013) proposed several factors that could contribute to the observed differences in language learning outcomes between adults and children. According to their explanation, these differences are not solely due to age, but are rather influenced by a range of factors that vary between individuals. For instance, differences in learning attitudes, such as motivation, engagement and interest in the language being learned, could play a significant role in shaping learning outcomes. Additionally, the duration and frequency of exposure to the second language may also affect learning 102 Celt: A Journal of Culture, English Language Teaching & Literature, Volume 22, Number 1, June 2022, pp. 96 – 113 https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ outcomes, as individuals who have more opportunities to use and practice the language are likely to achieve greater proficiency. Furthermore, cognitive factors such as working memory capacity, processing speed, and the ability to notice and form grammatical patterns could also contribute to the observed differences in learning outcomes. These factors can differ between individuals, and can influence how easily they learn a second language. Therefore, it is important to consider a range of factors that could contribute to the observed differences in language learning outcomes, rather than attributing them solely to age. Felix (1985) offers a different interpretation of the reason for the differences in language learning outcomes between adults and children. Felix posits that children have an advantage over adults in language learning because they are successful in acquiring their first language, while adults struggle to acquire a second language. Felix attributes this advantage to the presence of cognitive mechanisms such as the problem-solving system (PSC) and the language-specific cognitive system (LSC). Felix (1985) suggests that children have special mental mechanisms that allow them to internalize language learning more effectively than adults. This is because the language learning process is very complex and encourages conceptual abilities. In contrast, an individual with mature cognitive development may think conceptually, and the PSC mechanism replaces the role of LSC. Once PSC replaces LSC’s control, it is impossible to achieve full language abilities. It is important to note that Felix’s theory challenges the idea that age is the only factor that influences language learning outcomes. Instead, he argues that the cognitive mechanisms play a significant role in language learning, and these mechanisms may differ between children and adults. These differences may contribute to the variation in language learning outcomes between the two groups. Moreover, Felix’s view highlights the importance of cognitive development in language learning. It suggests that age-related changes in cognitive development may impact language learning outcomes. This implies that learners who are still in the process of cognitive development may have an advantage over adults in language learning. Additionally, the theory also emphasizes the need for language instruction that is appropriate for the learner’s cognitive development stage. Aziz, M.F., Jayaputri, H.E., Unpacking the Layers: Understanding The 103 Multifaceted Nature of L2 Learning Complexity https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ Al-Hoorie & Hiver (2020) noted that the Fundamental Difference Hypothesis (FDH) also emphasizes the distinction between how adults and children acquire language. According to the theory, there is a unique and inherent language acquisition mechanism in children that is absent in adults. Unlike Felix's theory, the FDH does not acknowledge the existence of the problem-solving system (PSC). Furthermore, the FDH posits that there is no potential for a role shift in second language learning, as even adults with negative attitudes and low motivation should still benefit from maximizing their language acquisition, which is not always the case. Although the theories of PSC and FDH contradict each other, Both of the theories propose the notion that language acquisition differs between children and adults due to distinct cognitive mechanisms. Adults use problem- solving abilities in language learning, which leads to language variations (Cardimona et al., 2016). Therefore, language variation is closely related to the various learning achievements of adults. In other words, both theories emphasize that the age at which language acquisition takes place plays an important role in determining the cognitive mechanisms used in language learning. While children have a unique and innate language acquisition mechanism, adults use their problem-solving abilities to acquire a new language. Therefore, adults tend to have language variations due to their different learning attitudes, motivation, and frequency of L2 acquisition. In other words, both theories emphasize that the age at which language acquisition takes place plays an important role in determining the cognitive mechanisms used in language learning. While children have a unique and innate language acquisition mechanism, adults use their problem-solving abilities to acquire a new language. Therefore, adults tend to have language variations due to their different learning attitudes, motivation, and frequency of L2 acquisition. Cardimona et al. (2016) assert that the gradual decrease in language skills is not limited to adulthood, but instead begins as early as 6 years old and continues up to the age of 16. However, Simon Sundström et al. (2014) conducted research suggesting that children who become bilingual or possess bilingual abilities, regardless of whether they do so early or simultaneously, may experience faster changes in language acquisition age-related declines. According to their argument, the timing of language learning experiences has a considerable effect on the perception of language sounds and pronunciation skills. Early language learning experiences can have a more significant impact on sound perception, while later experiences can affect the ability to produce 104 Celt: A Journal of Culture, English Language Teaching & Literature, Volume 22, Number 1, June 2022, pp. 96 – 113 https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ sounds more accurately. These results imply that language acquisition age and learning experiences can affect various aspects of language abilities differently. Therefore, when assessing individual variations in second language acquisition, it is crucial to consider these factors. Moreover, it has been observed that the previous exposure to a language has an influence on the brain mechanisms while learning another language. Recent studies using functional magnetic resonance imaging (fMRI) have shown that Chinese children who learn French as a monolingual between the ages of 6 to 36 months exhibit a similar pattern of brain activation as bilingual individuals (Pierce et al., 2015). This suggests that the early language learning experience can have a significant impact on how the brain processes and acquires language. The way a person perceives the sounds of their first language can affect their ability to learn the sounds of another language. This can cause difficulties for adults learning a second language, as their understanding of the new language's sounds is heavily influenced by their first language’s sounds. This suggests that the challenge in learning a second language lies more in the influence of the first language rather than biological limitations. The question of whether it is more advantageous to learn a second language before or after mastering the first language is worth exploring. Simon Sundström et al. (2014) argue that the influence of the first language on second language acquisition increases as the individual's abilities in the first language develop. As a result, it may be more feasible to learn a second language prior to attaining complete mastery of the first language. However, it is unclear how the second language system can be protected from the influence of the first language system during or after the critical periods. After considering the different perspectives presented earlier, it appears that there is no single theory that can fully account for the processes that occur during or after the critical period, particularly with regards to how the language system remains intact while still allowing for potential changes in language abilities. The preservation of the language system's integrity, especially in the absence of a distinct mechanism for adult language learning, is still a matter that needs addressing. C. The System Protecting Language Integrity The brain has a built-in mechanism that helps maintain the structure of a language system even as the language changes over time. Without this Aziz, M.F., Jayaputri, H.E., Unpacking the Layers: Understanding The 105 Multifaceted Nature of L2 Learning Complexity https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ mechanism, people's understanding and use of language would become increasingly different from each other. Contrary to previous beliefs about problem-solving abilities, researchers now think that this language defense mechanism may actually make it harder for adults to learn a second language. The mechanism tries to protect the first language system by interfering with the second language input that the adult brain is trying to absorb. Learning a new skill can be challenging due to our pre-existing ways of thinking. This was demonstrated in a National Geographic YouTube video, where a backwards bike was designed with handlebars that turned the opposite way. Participants, both children and adults, had difficulty riding it despite repeated attempts to control their balance. The video showed that "once we have a set way of thinking, it can be difficult to change even if we want to." Interestingly, children were able to learn to ride the backwards bike in just two weeks, while adults took 7-9 months. This suggests that learning a second language should prioritize ease of learning rather than speed. Children's brains have greater neuroplasticity, allowing them to adjust to new knowledge more easily than adults. However, with effort, adults can still restructure their brains to learn new skills or information. Schlegel et al. (2012) conducted a study on L2 Chinese learners and found that learning a second language can cause changes in the white matter of the brain. This study suggests that the flexibility of the language structure makes it easier for adults to learn a second language. However, the differences in brain capacities between adults and children cannot be fully explained by this finding. The researchers propose that there might be a language protection mechanism that safeguards the first language system, which is analogous to the immune system in the body. Similarly, just like the human immune system, which is underdeveloped at birth and matures over time to defend against various pathogens, the language defense mechanism appears to undergo a similar development (Simon et al., 2015, p.1). These mechanisms seek to protect the information stored in the first language system and affect the way a person internalizes a new language (Pierce et al., 2015). This aligns with the idea that language learning abilities gradually decline over time. Therefore, it may be easier to learn two languages simultaneously than to learn a second language after acquiring the first language. If language learning begins after the acquisition of the first language, the language defense system becomes stronger and intervenes with every new language input (Simon Sundström et al., 2014). This mechanism makes it 106 Celt: A Journal of Culture, English Language Teaching & Literature, Volume 22, Number 1, June 2022, pp. 96 – 113 https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ challenging to learn a second language and can lead to fossilization, where the first language system remains intact. See figure 1 The similarity between the immune mechanism and the language defense mechanism is represented in Figure 1. The growth of the language defense mechanism contributes to the decline in learning L2 ability, which is known as the fossilization phenomenon. This phenomenon leads language learners to rely on the L1 system, resulting in language errors caused by L1 interference (Ahibalova, 2019). On the contrary, L1 competence will keep developing without hindrance from the language defense mechanism even though language development varies during childhood and adulthood (Lightbown & Spada, 2013). This means that language development for individuals aged 1-12 years will differ from those aged 24-30 years. As age progresses, there is a corresponding development in L1 abilities such as ease in acquiring new L1 words, idioms, meanings, structures, and increasing L1 sociolinguistic abilities. As an individual grows older, it becomes more challenging to acquire a second language. It can be inferred that an individual's language ability will not decline if it relates to their L1 competence but will decrease if it is related to L2 competence. This suggests that there is a resistance to the enhancement of L2 ability. The language defense mechanism is responsible for maintaining the integrity of the L1 system and resists the improvement of L2 ability. This mechanism is closely linked to the L1 system and determines whether new language inputs are accepted or resisted. The mechanism adapts the new linguistic inputs to the L1 system. The concept that problem-solving abilities decline with biological maturity seems to contradict the fact that L1 abilities continue to grow. This idea was proposed by Ahibalova (2019). Despite the decline in problem-solving abilities, an individual's L1 ability to acquire new words, idioms, and meanings, as well as the mastery of new structures and sociolinguistic abilities, continues to develop over time. This suggests that L1 and L2 abilities are regulated by different mechanisms, and that the language defense mechanism, responsible for maintaining the integrity of the L1 system, has a greater impact on the acquisition of L2. The language defense mechanisms in the brain are responsible for maintaining the information of the first language, which in turn controls the enhancement of the second language. As a result, it resists the development of L2 abilities while L1 abilities continue to grow. In the process of learning, L2 Aziz, M.F., Jayaputri, H.E., Unpacking the Layers: Understanding The 107 Multifaceted Nature of L2 Learning Complexity https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ input is transformed into new linguistic intake, which is then processed by language learners (Kan et al., 2020). However, the language defense mechanism limits the linguistic intake or how it is processed. As long as the mechanism accepts new linguistic input, both L1 and L2 inputs can be processed into new linguistic intake. The mechanism works to monitor and regulate the linguistic inputs, and will adapt to the L1 system which either restricts or facilitates the internalization of L2. Figure 1: The progression of the language defense mechanism and its impact on the ability to learn L2 It has been observed that when a person learns a second language, the same neural areas of the brain get activated as when they are processing their native language (Weber et al., 2016). This suggests that the native language input influences the processing of the second language. However, this does not mean that the native language input constructs the intake of the second language. Instead, individuals are able to absorb and store two different language inputs, which is known as the concept of multi-competency (Cook, 2016, p.27). Thus, if the input of the new language is consistent with the existing native language information, it can facilitate the acquisition of the second language. The language defense mechanism is an inherent mechanism in the brain that functions to preserve native language information. Therefore, second language learning is not always hindered as long as the second language input corresponds with the native language information. Even if no linguistic input is absorbed, the language defense mechanism continues to perform its 108 Celt: A Journal of Culture, English Language Teaching & Literature, Volume 22, Number 1, June 2022, pp. 96 – 113 https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ role as a defense mechanism and does not depend on the presence of the second language input. However, the enhancement of second language ability is strongly affected by this mechanism. D. The Impact of Language Interference and Defense Mechanisms on L2 Learning The mechanism that protects the first language from being lost also affects the process of learning a second language, causing interference between the two languages. This interference often results in errors such as omitting, adding, overusing or underusing certain words or grammar structures. However, language interference may also provide some advantages for language learners. For instance, individuals from different linguistic backgrounds may find different aspects of learning a new language easier or harder. For instance, French students may find learning English easier than Arabic students because the French article structure is more similar to the English one, while the Arabic article structure is not. A study by Sarko (2009) supports this claim, as it found that native French and Arabic students studying L2 English achieved different results in their tests. Therefore, although language interference may negatively impact language learning, it can also facilitate it in some cases. Several studies indicate that language interference is related to defense mechanisms. For example, Wei & Zhang (2020) conducted a study on Chinese-speaking students learning English as a second language. They found that some students were unable to distinguish between the sentence structures in their first language and second language, which limited their ability to process new L2 input. Conversely, students who recognized the differences between the structures of their L1 and L2 were more successful in their language learning. The study suggests that there should be a specific approach to help students identify the differences between the two languages, as this can enhance their L2 abilities. This is crucial because the defense mechanism is more likely to retain new L2 input that is similar to L1 information. Therefore, recognizing the similarities between the two languages can help students improve their language learning. Regardless of the order of acquisition, studies have shown that learners can benefit from similar linguistic structures when they internalize input in L2. For example, Carvalho & da Silva (2006) conducted a study on bilinguals proficient in Spanish-English and English-Spanish, and concluded that knowledge of Spanish language was helpful in learning Portuguese for both groups, regardless of the order of acquisition. Additionally, the English- Aziz, M.F., Jayaputri, H.E., Unpacking the Layers: Understanding The 109 Multifaceted Nature of L2 Learning Complexity https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ Spanish bilinguals performed better than the Spanish-English bilinguals, likely due to their formal Spanish education and metalinguistic knowledge. These findings support the results of Wei & Zhang's (2020) research. Foucart & Frenck-Mestre's (2011) research also shows that the similarity of syntactic structures and perception between German and French affects language behavior. The defense mechanism interacts with L1 information, shaping how learners compare the two linguistic structures. According to Weber et al. (2016), when Dutch students were exposed to language input that contained artificial structures, brain activity was more pronounced when the language structure differed from their native language as compared to when it was similar. This supports the idea that the native language can aid in the mapping of new language. Furthermore, the study found similarities in brain activity patterns during the internalization of the artificial language structure and the participants' native language when some aspects of the artificial structure corresponded with their native language structure. Although language structure similarities and differences play a role in L2 learning, they are not the only decisive factor for L2 achievement. The defense mechanism is not exclusively influenced by the similarity of the two language structures as they are complex and continuously interact. Rather, the defense mechanism focuses on whether the new language input hinders the integrity of L1 information. Furthermore, when interacting with L2 input, the defense mechanism also alters the L1 structure due to the L1 system's integrity. CONCLUSION The present study discusses the language defense mechanism as an inherent process that preserves the integrity of one's native language. This mechanism checks and rejects new linguistic input that might harm the L1 information. As people age, L1 proficiency strengthens due to this mechanism. As a result, the defense mechanism can be used to address challenges in L2 learning such as language interference, fossilization, and ease of learning a new language. Future research should investigate whether reducing the defense mechanism by emphasizing similarities between different language structures can enhance L2 learning outcomes. Such research can provide evidence that language interference can have a positive influence on language acquisition. 110 Celt: A Journal of Culture, English Language Teaching & Literature, Volume 22, Number 1, June 2022, pp. 96 – 113 https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ REFERENCES Ahibalova, T. (2019). Fossilization in adult second language acquisition. Scientific Notes of Ostroh Academy National University: Philology Series, 6(74), 150–153. https://journals.oa.edu.ua/Philology/article/view/2476 Al-Hoorie, A. H., & Hiver, P. (2020). The Fundamental Difference Hypothesis: Expanding the Conversation in Language Learning Motivation. SAGE Open, 10(3). https://doi.org/10.1177/2158244020945702 Arifin, W. L. (2016). Interference: Its Role in the Target Language Mastery to Indonesian Learners. Register Journal, 4(1), 91–108. https://doi.org/10.18326/rgt.v4i1.91-108 Bialystok, E., & Miller, B. (1999). The problem of age in second‐ language acquisiton: Influences from language, structure, and task. Bilingualism: Language and Cognition, 2(2), 127–145. https://doi.org/10.1017/S1366728999000231 Bohn, M., Kachel, G., & Tomasello, M. (2019). Young Children Spontaneously Recreate Core Properties of Language in A New Modality. Proceedings of the National Academy of Sciences of the United States of America, 116(51), 26072–26077. https://doi.org/10.1073/pnas.1904871116 Cardimona, K., Smith, P. A., & Roberts, L. S. (2016). Lexical Organization in Second Language Acquisition: Does the Critical Period Matter? Tesol Journal, 7(3), 540–565. https://doi.org/10.1002/tesj.219 Carvalho, A. M., & da Silva, A. J. B. (2006). Cross–linguistic influence in third language acquisition: The case of Spanish–English bilinguals’ acquisition of Portuguese. Foreign Language Annals, 39(2), 185–202. https://doi.org/10.1111/j.1944–9720.2006.tb02261.x Cook, V. (2016). Second Language Learning and Language Teaching (5th ed.). Routledge. https://doi.org/10.4324/9781315883113 Denman, D., Speyer, R., Munro, N., Pearce, W. M., Chen, Y.-W., & Cordier, R. (2017). Psychometric Properties of Language Assessments for Children Aged 4–12 Years: A Systematic Review. Front. Psychol, 8(1515), 1–28. https://doi.org/10.3389/fpsyg.2017.01515 Aziz, M.F., Jayaputri, H.E., Unpacking the Layers: Understanding The 111 Multifaceted Nature of L2 Learning Complexity https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ Felix, S. W. (1985). More evidence on competing cognitive systems. Second Language Research, 1(1), 47–72. https://doi.org/10.1177/026765838500100104 Foucart, A., & Frenck-Mestre, C. (2011). Grammatical Gender Processing in L2: Electrophysiological Evidence of the Effect of L1-L2 Syntactic Similarity. Bilingualism: Language and Cognition, 14(3), 379–399. https://doi.org/10.1017/S136672891000012X Ghalebi, S. R., & Sadighi, F. (2015). The Usage-based Theory of Language Acquisition: A review of Major Issues. Journal of Applied Linguistics and Language Research, 2(6), 190–195. http://www.jallr.com/index.php/JALLR/article/view/138 Ginting, S. A. (2019). Lexical Formation Error in the Descriptive Writing of Indonesian Tertiary EFL Learners. International Journal of Linguistics, Literature and Translation, 2(1), 85–89. https://doi.org/10.32996/ijllt.2019.2.1.11 Kan, P. F., Miller, A., Cheung, S., & Brickman, A. (2020). Intake factors and intake processes in adult language learning. Language, Speech, and Hearing Services in Schools, 51(4), 1007–1023. https://doi.org/10.1044/2020_LSHSS-19-00112 Koster, D. (2015). A dynamic, usage-based approach to teaching L2 Dutch. Dietha Koster, 4(2), 257–264. https://doi.org/10.1075/dujal.4.2.08kos Lightbown, P. M., & Spada, N. (2013). How languages are learned. Oxford University Press. Long, M. (2013). Maturational constraints on child and adult SLA. In G. Granena & M. Long (Eds.), Sensitive periods, language aptitude, and ultimate L2 attainment (pp. 3–42). John Benjamins. https://doi.org/10.1075/lllt.35.01lon Mair, C. (2015). Parallel corpora. A real-time approach to the study of language change in progress. Diacronica: Impavidi Progrediamur, 1(6), 1–9. https://doi.org/10.17684/i1A6en Mendívil-Giró, J. L. (2019). Did language evolve through language change? On language change, language evolution and grammaticalization theory. Glossa: A Journal of General Linguistics, 4(1), 124. https://doi.org/10.5334/gjgl.895 112 Celt: A Journal of Culture, English Language Teaching & Literature, Volume 22, Number 1, June 2022, pp. 96 – 113 https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ Nevalainen, T., & Raumolin-Brunberg, H. (2017). Nevalainen, T., & Raumolin-Brunberg, H. (2017). Sociolinguistics and Language History: The Helsinki Corpus of Early English Correspondence. HERMES: Journal of Language and Communication in Business, 7(13), 135–143. https://doi.org/10.7146/hjlcb.v7i13.25079 Newport, E. L. (2018). Is there a critical period for L1 but not L2? Bilingualism: Language and Cognition, 21(5), 928–929. https://doi.org/10.1017/S1366728918000305 Pierce, L. J., Chen, J., Delcenserie, A., Genesee, F., & Klein, D. (2015). Past experience shapes ongoing neural patterns for language. Nature Communications, 6(10073), 1–11. https://doi.org/10.1038/ncomms10073 Sarko, G. (2009). L2 English article production by Arabic and French speakers. In M. P. Garcia Mayo & R. Hawkins (Eds.), Second language acquisition of articles: Empirical findings and theoretical implications (pp. 37–66). John Benjamins. Schlegel, A. A., Rudelson, J. J., & Tse, P. U. (2012). White matter structure changes as adults learn a second language. Journal of Cognitive Neuroscience, 24(8), 1664–1670. https://doi.org/10.1162/jocn_a_00240 Schmid, M. S. (2014). The Debate on Maturational Constraints in Bilingual Development: A Perspective from First-Language Attrition. Language Acquisition. Language Acquisition, 21(4), 386–410. https://doi.org/10.1080/10489223.2014.892947 Septina Sulistyaningrum, E. A. (2020). Aspects of Language Error at Morphological Level in Students’ Descriptive Texts. Proceedings of the Third International Seminar on Recent Language, Literature, and Local Culture Studies, 1–6. http://dx.doi.org/10.4108/eai.20-9-2019.2296725 Simon, A. K., Hollander, G. A., & McMichael, A. (2015). Evolution of the immune system in humans from infancy to old age. Proceedings of the Royal Society, 1–9. https://doi.org/10.1098/rspb.2014.3085 Simon Sundström, Samuelsson, C., & Lyxell, B. (2014). Repetition of words and non-words in typically developing children: The role of prosody. First Language, 34(5), 428–449. https://doi.org/10.1177/0142723714550213 Aziz, M.F., Jayaputri, H.E., Unpacking the Layers: Understanding The 113 Multifaceted Nature of L2 Learning Complexity https://doi.org/10.24167/celt.v22i1; ISSN: 1412-3320 (print); ISSN: 2502-4914 (online); Accredited; DOAJ Weber, K., Christiansen, M. H., Petersson, K. M., Indefrey, P., & Hagoort, P. (2016). fMRI Syntactic and Lexical Repetition Effects Reveal the Initial Stages of Learning a New Language. Journal of Neuroscience, 36 36 (26)(26), 6872–6880. https://doi.org/10.1523/JNEUROSCI.3180- 15.2016 Wei, X., & Zhang, W. (2020). Investigating L2 writers’ metacognitive awareness about L1-L2 rhetorical differences. Journal of English for Academic Purposes, 46(100875). https://doi.org/10.1016/j.jeap.2020.100875