It is popularly assumed that native-like fluency of a second language can only be achieved if a child is exposed to it before 7 years old. Not only is this belief incorrect, but the cognitive advantages of the bilingual experience can span our entire lives. 

There are two main differences between learning a second language as a monolingual person and as a simultaneous bilingual person, someone who learns two or more languages from birth. Bilingual infants perform computations that their monolingual counterparts do not need to execute, such as language discrimination, or recognizing multiple types of speech being spoken in the same environment. One study found that bilingual infants could differentiate between languages when watching a silent video even if they had never been exposed to them, while monolingual infants could not. This demonstrates a specific adaptation in the attentional system, allowing bilingual infants to perceive and track information in separate, but parallel, language systems. It is theorized that due to the increased language processing demands of learning two languages, bilinguals experience more effortful processing of their second language, which manifests as more frequent “tip-of-the-tongue” states or slightly slower rate of speech.

According to the National Library of Medicine (NIH), the neural representations employed when bilinguals use either language are similar. When learning a language in general, infants must learn the phonemes, words, definitions, grammar, and more. This task increases twofold for bilingual infants, who must learn two sets of linguistic codes instead of one, and with reduced exposure to both. These extraneous processes may help support the finding of simultaneous bilingual infants who demonstrated the ability to switch their attention in non-linguistic tasks more efficiently at seven months old and had more developed memory generalization processes at 18 months old compared to their monolingual counterparts. 

Additionally, the University of Houston identified that bilingual children performed better than monolingual children in executive functioning, which is a set of mental functions outlining our use of flexible thinking, self-control, and working memory. This is linked with higher classroom success. They were able to inhibit preferred patterns of responding, like sitting when instructed instead of jumping around.

Improved executive function can be attributed to language co-activation. When bilingual individuals use one language, the other language system is active at the same time. To maintain balance between the two languages, the bilingual brain must practice executive function by using control mechanisms that inhibit or excite a certain language system, allowing the individual to choose the correct language. This is a mental exercise that strengthens the brain through repetition. Because they can tap into their inhibitory control ability, bilingual individuals often perform better on conflict management tasks. Language co-activation is also linked to neuroplasticity, the brain’s ability to change and adapt its structure and function in response to environmental stimuli.

The cognitive benefits of bilingualism do not stop in infancy—they extend throughout the lifetime. Learning a second language is proven to promote cognitive reserve in elderly people, preserving efficient utilization of brain networks and enhancing brain function during aging. They were found to outperform monolinguals in memory and executive control tasks. Perhaps even more remarkably, researchers identified a link between bilingualism and delayed behavioral symptoms associated with neurodegenerative disorders like Alzheimer’s disease. The age of bilingual individuals at the onset of the disease and the age at their first medical appointment related to cognitive symptoms of dementia were 4-5 years later than monolingual individuals.

Although most studies have been done on simultaneous bilinguals, it is still not too late to start learning a second language! Restart your Duolingo journey, ask your parents to speak your native language to you instead of English, or watch content from a foreign country. Bilingualism promotes healthy cognitive aging, something we can all strive for.