Here I am. A small confused boy. My mum is Czech and my daddy is German. Together they speak most of the time English. My two big sisters are Czech who understand and speak some English, but with me, they speak mainly via smiles. To make it even worse, my uncle is Czech, but my aunt is Spanish. Their daughter speaks a weird Spanish-Czech language. Other aunt is German, and her boyfriend Portuguesse…. It is really difficult to understand this world and people in it. For now, I am mainly silent. Observing and listening. Laughing a lot and sometimes screaming when I get frustrated. People sometimes say that I am a poor guy and that I have it tough. But my mum and dad say that I do not have to worry, that I will learn to understand them as quickly as other kids and on top, I will be able to speak with more kids around the world.
Every year, there is an increased number of marriages of couples speaking different languages. On top of that, add immigrants, and people who just want to teach their kids a foreign language as soon as possible. Raising a kid in bilingual or trilingual settings is not anymore the specialty of Switzerland. Did you know that Tucanoan people (in Amazonia) are all native bilinguals? How is that possible? They practice the so-called linguistic exogamy rule, which means, that each marriage has to happen outside the linguistic community .
Maybe you have the same feeling as many other people, that kids in bilingual or trilingual families have it harder. How many times have I heard the sentence “Oh, what a poor guy,” which was trying to point out how hard it is for our son to learn a language in our trilingual family. The old belief that speaking to kids in different languages will negatively impact their learning and understanding of language is not valid anymore. Today we know, that not only that they are able to manage to easily distinguish between languages and learn with the same speed as monolinguals, but also that multilingualism affects the structure and functioning of the brain, having a positive effect on cognitive processes as well as protecting the brain from the cognitive decay.
The belief that multilingualism has negative impact on language acquisition was based on the belief that for the infant, all the languages are part of one language and therefore they are only able to separate them after establishing initial lexicon and syntax . But already in 1962  an experiment showed that bilingual children outperformed monolinguals in both verbal and non-verbal intelligence tests. From the recent research it seems that infants are able to separate languages right from their birth using various approaches. The native speakers can distinguish native language from another language which is in different rhythmical classes already at birth  and the ones from the same rhythmical class at 4-5 months. Bilingual kids can do the same for both of their native languages. It seems that distinguishing between various languages is way easier for bilingual infants than it was believed. They use visual cues, phonological and lexical differences, as well as a specific stress pattern of the individual languages.
In one of the studies, they found out that bilingual newborns are able to distinguish various languages from each other, even when the speakers are muted. It seems that what they hear and how they process this information differ from monolingual kids. Both native monolinguals and bilinguals can distinguish the native language only based on visual cues at 4 months , but the learners who learned the second language later in life, never get the same skill and score only at chance level. Seemingly, bilingual children are more sensitive to even small facial distinctions as they keep a very good level of discriminating the native language among languages, keeping the skill to discriminate the native language only based on the visual cues during the lifetime.
Bilingual children are also able to distinguish languages using phonological and lexical differences better than monolingual kids.  For example, one study showed that bilingual children are able to distinguish Spanish and Catalan vowels not only at 4 months as monolingual kids do but also at 12 months. Also, Japanese adults who were raised as bilingual or learnt English early can distinguish between English “r” and “l”, which is not possible for late English learners.
Another help for distinguishing languages is a stress pattern. For every language, there is a different stress pattern and the native stress pattern helps you to segment words from each other, which is crucial for language acquisition. If a kid is learning only one language, it learns the given stress pattern and then shows a preference for the native stress pattern. How the stress pattern is important was shown in one study , where they tried to teach to kids associations between phonological dissimilar or similar nonsense words, and bilingual kids succeeded later than monolinguals.
To summarize, it seems that the language processing for bilingual infants and the way they process and acquire language is unique.
I tried to speak a bit, but it was really difficult with my parents. I learned to say the word “Cojeto” (“Co je to” is “What is it?” in Czech), but my father sometimes didn’t understand what I wanted. Then I better learned to point with my finger to things and make noise — it seemed to finally work (hurray, I found an international way of communication!). Anyway, even pointing can be quite frustrating with my parents. Sometimes they are so stubborn. Fortunately, training helps and they get better every day. I tried few more words without much success. Then I found “Nenene” (“no” in Czech), which is a lot of fun, and “brm brm” to tell them that I see a car or that I want to go on wheels and I was sooo happy when they finally both understood what I meant. When I am in a good mood, I say “ja” (“yes” in German). Luckily I can call them “mama” and “tata” and then they come smiling to me and hug me. Or we just play a “baf” game and I fall on my bottom from how much I have to laugh. Then I forget my frustration from not being able to tell what I want.
It might seem that the bilinguals start to speak later and their vocabulary is smaller, but this feeling is not based on any real studies. When summing up the words from both languages, it seems that the vocabulary of both bilingual/trilingual and monolingual children has the same size . It seems smaller only because they mix the words (code mixing) from both languages. Why they do so? Mixing words makes total sense – they have only restricted capacity for new words and they do not have a capacity to learn each word in both languages [11, 11b]. Later, when their vocabulary grows, they easily separate these languages .
There is one really funny thing about my parents. When we go around a dog, a pig, or a cow, they try to make the sound of the animal. But their animals always make different sounds. Mum says “haf haf”, “chro chro”, or “bú bú” and daddy says “wuff wuff”, “oink oink“ and “muh muh”. The funniest thing is when they see a sheep and daddy says to me: “Mäh mäh”. Then my mum starts complaining: “This is not a goat which makes ‘mé mé’, this is a sheep and it makes ‘bé bé’.” Isn’t it funny? To me every sheep sounds different, some say more “mäh mäh” and some say rather “bé bé”. But maybe when I will grow up, I will finally hear them properly and then I can tell my parents which of them is more right.
Raising bilingual children can be done in several ways and it is not clear which one is more effective or better . You can use one-person-one-language strategy (OPOL, each of the parents speaks consistently with one language), Minority language at home (MLAH, speaking one language at home and the one which dominates in country, in all the other occasions), or Time and place approach (T & P, speaking the second language in given times and situations). The selection of the strategy might depend on if you are fluent in all the languages and which language is the majority language in the country. Anyway it is important to note, that it was shown that the kid is not getting confused even when the same parent is switching between different languages as there are many cues that help the kid to distinguish which language is currently spoken, so do not be worried too much that you might confuse your kid. What is important is to expose the kid enough to the foreign language.
Some people around say that I will have a big advantage from being multilingual. They speak a language which I do not understand. They say that my brain is developing in a special way to maintain multiple languages and therefore it will gain a higher structural and functional plasticity also for other tasks, improving my learning and memory skills. That because my brain has to manage to switch between multiple languages, it develops enhanced executive control abilities. I am not sure what it should mean, but I guess it is good. I also heard some other things which I really did not understand – that recovery of my linguistic skills after a stroke might be quicker and that I might get a later onset of Alzheimer. Hmm, but how is all of this useful to me when I am not able to talk? When I have no way to tell my parents what I want? I would give anything to be able to speak to them. But which word should I select? Czech, English, German? I always think about starting to speak but then immediately I am voiceless. My mum cuddles me and tells me that I should not worry about it, that starting to speak a bit later is normal and that all the advantages will overgrow this small negative. I want to trust her. But anyway, I still would like to speak right now! At least I can understand what my parents are telling me. I also question myself, if kids on a playground will understand me. I understand them. But will they understand me?
Recent studies have shown that bilingual children have improved efficiency of cognitive processing and are better protected from cognitive decline compared to monolinguals. It seems that the necessity to manage multiple languages train the kids’ brain from the early beginning and leads to permanent changes of the brain of these kids. The bilingualism seems to contribute to neuroplasticity, which protects them from cognitive decline (e.g., the onset of dementia is on average 4 years later for bilinguals than monolinguals , delayed onset of Alzheimer disease [16, 16b, 16c], etc.).
What exactly happens in the brain of bilinguals? Recent studies using neuroimaging methods reveal that there are several modifications of their brains, enabling them to rely on more efficient processes for cognitive tasks. In the brain of bilinguals, both languages are jointly activated  and compete for selection, possessing big challenges and training for the brain. Bilinguals show greater gray matter volume especially in perceptual/motor regions . In parallel there is evidence that they also have greater white matter (WM) integrity  which might explain why bilinguals outperform monolinguals in the tasks when the quick response time is needed. Furthermore, they have stronger functional connectivity between brain regions, enabling more efficient distribution of the work within the brain. There was also measured less frontal activation during execution of nonverbal tasks, suggesting that managing mental tasks costs them less energy and that they are able to better distribute the work within the brain and work more effectively. [20, 21]
And what about trilingualism? That is not that easy to say. In general, we might expect that when a person is repeatedly faced with a challenging task, it should exhibit improvements in a cognitive processes. This was observed in many cases starting with action video games to playing a musical instrument. Nevertheless, if the cognitive demand is too high, it might not lead to a better performance. In the same way, we might see a bilingualism and trilingualism. There is various evidence on if trilingualism actually has benefits over bilingualism or not . It seems, that in some cases, it might have even higher benefits than bilingualism (such as a greater cognitive reserve in adults, [23, 24].), sometimes the benefits are the same (such as in inhibitory control [25, 26]), and in some cases, it even fails to show the benefits observed for bilingual kids (e.g. toddlers and infants do not show the same benefits in memory generalization tasks as bilingual babies [27, 28].).
To summarize, it seems quite clear that the benefits of multilingualism definitely outweigh the negatives. Learning multiple languages in childhood causes several functional and structural changes in their brain which delay the cognitive decay and improve the executive cognitive processes. The benefits are the strongest for the early learners but it is never too late to train your brain :-).
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