Bilingualism is a person's ability to use two languages in everyday life. An estimated 1 in 3 people are bilingual or multilingual. In California, United States, it is estimated that by 2035 more than 50% of children who have just entered kindergarten will be bilingual.

Bilingualism in Child Development: Benefits and Scientific Evidence
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There is a concern that children with bilingual will experience language confusion or impaired brain development, which will affect their social and cognitive performance. However, often this concern is not based on scientific evidence but assumptions and hunches. One of the most prominent is the opinion that bilingual children tend to experience language confusion and even speech delay.

Opinions about the language confusion often arise because bilingual children combine two languages in one sentence (code-mixing). In fact, code-mixing is part of normal language development.
Why do bilingual children do code-mixing? The reasons are :

  1. Children imitate the adults' behavior around them, who also often combine two languages in one sentence.
  2. Normal limitation on vocabulary. Like monolingual children, if bilingual children cannot quickly find the right word to describe an object in one language, they will call it another language.
Byers-Heinlein et al. argued that code-mixing should not be considered as language confusion, but rather the bilingual child's ingenuity in expressing the meaning of their thoughts.


Benefits of Bilingualism

The use of language in an integrated and sustainable manner will affect children's brain structure and cognitive abilities. Thus, bilingualism benefits are limited to verbal communication and involve all other brain activities, including learning abilities.

The brain's plasticity in early life allows the brain to accept all the information introduced at that time, including language. Exposure to more than one language at the beginning of brain development increases the stimulus and plays a good role in subsequent brain development.

One of the factors that influence language development in children is the stimulation of heard sounds. When babies are introduced to only one language, the brain area is thought to be sensitive to that one language only. Conversely, when babies are introduced to more than one language early on, language centers' sensitivity in the brain is thought to be more varied and allows for better development.



Scientific Evidence Regarding Bilingualism and Brain Development

Blom et al. conducted a study to determine whether there were differences in visuospatial and verbal working memory abilities between monolingual and bilingual children. This study involved 68 Dutch-Turkish bilingual children and 52 monolingual Dutch children. They found that children in the bilingual group had a cognitive advantage in visuospatial and verbal working memory tests, particularly on tests that required processing rather than just storage.

Another study showed that the bilingual children group with equal proficiency in 2 languages has a thinner brain cortex structure and a larger putamen structure than the bilingual children group who have a difference in proficiency between their mother tongue and their second language. The group of children who did not have equal proficiency in both languages ​​was also found to have a smaller cortex surface area than the group with equal proficiency. The clinical effect of these findings is not known.

Several studies show that bilingual children have better statistical learning abilities upon entering school age than children who only speak one language. However, there are no studies that can explain the causal relationship directly.



Summary
Bilingualism is often associated with worrying about language confusion or even speech delay. However, these concerns are generally not based on scientific evidence but myths and misinterpretations. Various scientific evidence that has been described in the article above shows that bilingualism has a good effect on children's brain development, including memory and cognition. However, there is no strong evidence related to a cause-and-effect.