Statistics have shown that only a small portion of the world's population is multilingual, or the ability to be highly proficient in multiple spoken and written languages. However, since the beginning of 21, there has been a trend of an increasing number of multilingual people. century. For example, governments in East Asian countries have focused on foreign language programs in primary and secondary education in recent decades. Studies have been conducted to find out the most suitable age for people to study other languages, and one of the studies shows that only children who started learning their second language before the age of fifteen can fully achieve the native pronunciation of that language ( Lightbown & Spada, 2013, p. 94). Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay Despite those who have learned several native languages ​​already in early childhood, there are many teenagers who begin to learn foreign languages ​​​​guided by their parents. Most parents, however, may not fully understand the actual differences between children who are capable of mastering multiple languages ​​and those who are not. It is therefore necessary for public opinion to recognize the advantages that multilingualism can offer. Multilingualism is beneficial to adolescents before age 15 because they may have more cultural and educational opportunities, better cognitive abilities including memorization, information processing, and executive functions, and greater communication skills. For starters, the ability to speak multiple languages ​​provides more cultural and educational opportunities for teens. First, multilingual adolescents can gain more cultural opportunities. Because language is one of the most common and important tools for human interactions and self-expression, it is often called the foundation of a culture. Therefore, learning a language can help you understand its historical and cultural context. According to Angela Scanrino (2014), by learning and using a different language, adolescents can interpret a different part of the distinct culture (Scanrino, 2014, p. 391). Scanrino (2014) further stated that the study of new languages ​​emphasizes cultural practices in which people generate, clarify, and reflect their own cultural involvements (Scanrino, 2014, p. 390). By being able to speak multiple languages ​​fluently, children are more likely to have multiple cross-cultural experiences. Understanding their native language when traveling or living in another country allows them to explore and communicate with local communities in a deeper way. According to a Japanese undergraduate student at the University of Wisconsin-Madison, he spent his early childhood in Japan, but started living in China for five years when he was nine years old, and later went to the United States of America. Because his father had grown up in a traditional Japanese family and his mother had lived in China for her early twenties, living in a combination of two distinct environments allowed him to learn both languages ​​and cultures throughout his childhood. Furthermore, the reason he was able to experience American culture was that he was able to live with a standard American family during his four years of high school. Therefore, he was involved in three distinct types of companies. He thinks that the variety of cultural experiences has allowed him to understand things in a deeper aspect, thus helping him to form a healthy self-esteem. For example, he learned the importance of conscientiousness and self-independence from Japan, the importance of hard work from China, and the benefits of opinionsliberals and critical thinkers from America. Furthermore, frequently changed living environments can improve a fifteen-year-old adolescent's adaptability and flexibility. Despite the cultural opportunities they may receive from multilingualism, multilingual adolescents can benefit from obtaining additional educational opportunities, and one of the greatest opportunities is the chance to study abroad. Regardless of countries with the exact same native language, most countries in the world have different official languages. Therefore, multilingualism is a determining factor in deciding whether a student is selected to participate in the study abroad program or not. Additionally, having the opportunity to study abroad in a completely different country can change a child's future life. For example, a South Korean student named Jin Yong Choi learned English as a second language and began studying abroad in America at age 14; four years later, he was accepted by the University of Illinois at Urbana-Champaign. He explained that the reason he studied abroad was that he was dissatisfied with the traditional Korean education system, which is inflexible and restrictive, and that the overly competitive environment in Korea left him no choice but to study outside the country. He said that studying abroad at the age of fourteen was an irreplaceable experience for him. In his four years of American high school, his academic experience was more flexible: he could choose the courses he liked, the academic environment was intense but not overly competitive, and he was able to develop his interests during his free time. . He doubted that he could be accepted by UIUC without studying abroad in America for high school (Phuong, 2008). According to statistics provided by Phuong, among the approximately 576 South Korean students accepted by UIUC in 2008, 346 of them had graduated from a US high school (Phuong, 2008). Therefore, it is useful to have study abroad experience, and the ability to speak multiple languages ​​is the premise of such opportunities. Additionally, multilingualism benefits adolescents with their cognitive abilities that include memorization, information processing, and executive functions. First, learning another language can strengthen your content retention and information processing skills, which is how quickly your brain processes information. Most languages ​​are made up of rules such as spelling and grammar, and adolescents under fifteen can gain the ability to transfer that knowledge into automated information by practicing. In a book titled “How Languages ​​Are Learned,” Professor Lightbown et al. wrote that Robert DeKeyser (1998, 2001, 2007), a researcher at the University of Maryland, defined "declarative knowledge" as the rules of the language that students are aware of having, and "procedural knowledge" as the ability to use the language . Lightbown et al. continued that through practice, students can find the pattern among declarative knowledge and gradually move from memorizing declarative knowledge to mastering procedural knowledge (Lightbown & Spada, 2013, p. 109). The process of transferring declarative knowledge into the train of procedural knowledge allows the brain to improve its memory capacity. Also Lightbown et al. spoke of the “observation hypothesis” proposed by Richard Schmidt (1990, 2001), which implies that observation is the initial critical point of memorization (Lightbown & Spada, 2013, p. 115). By gaining more procedural knowledge within the brain, sentences and grammar get noticedconstantly can create a stronger storage coding and storage system. In addition to the advantageous storage system, the connection speed can also be improved by learning a new language. Lightbown et al. wrote that an expert speaker of multiple languages ​​builds a greater network of connections between linguistic features through practices (Lightbown & Spada, 2013, p. 111). Therefore, by associating information together, students are able to think and react faster. Furthermore, Lightbown et al. wrote about a study conducted by Jacqueline Johnson and Elissa Newport (1989). The study tested 46 Chinese and Korean speakers who began learning English as a second language at separate ages. They are asked to decide whether there are grammatical or spelling errors in several complete sentences and to match their answer to twelve main categories. The result shows that people who started learning English at an early age received the highest scores (Lightbown & Spada, 2013, p. 95). This is because people who became multilingual during childhood and adolescence benefited the most from procedural knowledge and were able to build a comprehensive network of associations in their brains. Not only can multilingualism improve their storage and information processing skills as part of cognitive abilities, but adolescents may also possess stronger executive functions. Executive functions are cognitive processes that include selections, attention and cognitive flexibility. These are crucial skills for adolescents because they are closely linked to their thinking, reasoning and visual processes. According to Raluca Barac and Ellen Bialystok, there are studies from the last decades that provide clear evidence that multilingualism before peak age has no relationship with the growth of intelligence but has enormous positive effects on the development of executive functions (Barac & Bialystok, 2011, p. 37). One of the research was conducted in Switzerland by Lewis Balkan (1970), professor at the University of Brussels. Balkan created several non-verbal tests capable of precisely measuring cognitive flexibility in three controlled groups: participants in the first group became bilingual before the age of 4; the participants in the second group became bilingual between the ages of 4 and 14; and the participants in the last group are monolingual. The results show that the first and second groups perform significantly higher than the third group. (Diaz, 1983, p. 36). Therefore, multilingualism has an extremely positive influence on cognitive abilities, including memorization, information processing and executive functions. Additionally, multilingualism is beneficial to adolescents' communication skills. Switching between languages ​​often allows adolescents to improve their ability to understand other people's points and express their own opinion, thus strengthening their communication skills. In the book “How Languages ​​Are Learned,” Lightbown et al. wrote about the interaction hypothesis reviewed by Michael Long (1996), professor of second language acquisition at the University of Maryland, College Park. Long argued that communication is an effective way to improve language skills because when speakers try to express an idea, they overhear and compromise the meaning, and this negotiation is beneficial to their language development (Lightbown & Spada, 2013 , p. 114). Therefore, interlocutors will be able to express their opinions more clearly and with less hesitation in the future. Furthermore, research conducted by the University of Chicago and Cornell University has shown that even minimal learningMultilingual can affect children's abilities to understand and communicate. Sixty-four children aged between 14 and 17 months were part of the experiment, in which half of them were exposed to an additional language other than English, while others were not. On a table, two randomly selected toys, one is visible to both the experimenter and the child, and the other is visible only to the child. The experimenter then asked the child to hand him the toy he could see. For example, suppose the two toys are a toy car and a teddy bear, and the experimenter can see a toy car but not the teddy bear, he or she will ask, “Ooh, I see a car, can you hand me the car please?” Two trials were carried out for both groups, one with two different toys and the other with identical toys. The results showed that the multilingual group averaged 0.683 corrections while the monolingual group averaged 0.553 corrections, so the multilingual group had 10% better accuracy than the monolingual group (Liberman, WoodWard, Keysar, & Kinzler, 2017 ). Therefore, they concluded that being multilingual for younger children could improve their communication skills. However, there are opposing views regarding whether multilingualism may contribute to neurodevelopmental disorders. Since the rational part of the average teenager's brain is not fully developed and will not be until age 25, learning multiple languages ​​could have negative effects on his or her neural system. Uljarevic et al. (2016) stated that learning multiple languages ​​could be difficult and overwhelming for some children and cause neurodevelopmental disorders (Uljarevic, Katsos, Hudry, & Gibson, p. 1205). However, no study has clearly demonstrated the negative correlation between multilingualism and neurodevelopment. Uljarevic et al. searched through 597 peer-reviewed studies on multilingualism and neurodevelopment. They first removed 465 after reading the abstracts, and then further removed 82 studies due to non-experimental methods, irrelevant research samples, and inconsistent discussions. Of the fifty studies remaining, more than half were tested on language performance, ten studies were tested on language functioning, and the remainder of the studies were tested on other neurodevelopmental disorders such as intellectual disabilities. The results showed that 94% of the studies concluded that there is no relationship between multilingualism and neurodevelopmental disorders, while three studies concluded that multilingualism can have a positive influence on language performance (Uljarevic, Katsos, Hudry, & Gibson, 2016 , p. 1211). Therefore, there is no evidence to support that multilingualism contributes to neurodevelopmental disorders in adolescents under the age of fifteen. Additionally, parents and researchers worry that learning multiple languages ​​for children with ASD could further harm their communication skills. ASD, short for autism spectrum disorder, is the disorder that causes problems with communication and social interaction. They fear that learning additional languages ​​will prolong their delays in social interactions. However, studies have shown that there is no evidence to support an association between multilingualism and further communication impairments. In a study conducted by Simon Fraser University, a sample of 174 children aged between 6 and 16 years with ASD were monitored, half of whom were multilingual and the other half monolingual. The results showed that there is a statistical difference in communication skills between two groups regarding their disorders. However, there is a negligible difference.