Can you forget your native language?

A native language, or "mother tongue," is the first language a person learns and is usually a key part of their identity, allowing them to connect with their family and friends and to embrace their culture and heritage.

But is it possible to forget your native language — for example, if you move to another region or country and start speaking a different dialect or language?

Linguists call this phenomenon "native language attrition," or the process in which you become less competent in your native language over time — perhaps because you're not using it as much.

Experts say it's possible to forget your native language in certain circumstances, particularly in the case of young children moving to a different country or region where a different language is spoken.

A prime example of this are young children who are adopted by families who live in other countries. For instance, a 2003 study in the journal Cerebral Cortex found that children who were born in Korea but were adopted by French families when they were between the ages of 3 and 8 were no better at understanding Korean at age 30 than native French speakers who'd never been exposed to the language.

However, the older you are when you move, the greater the likelihood that you'll keep your native language because you'll have established a much more solid grounding in it, Laura Dominguez, a professor of linguistics at the University of Southampton in the U.K., told Live Science. Therefore, it's improbable that a teenager or an adult would forget whole chunks of language, like how to construct the past tense, she said.

Indeed, research suggests that people are less susceptible to native language attrition after they hit puberty (between the ages of 8 and 13 in girls and 9 and 14 in boys). This is probably because beyond this age, our brains mature and become less malleable and receptive to change.

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That said, the part of your native language that is most vulnerable to being lost even after short periods is vocabulary, Dominguez said.

For instance, say you're an English-speaking college student who has spent a semester abroad in Spain. You may find that when you come back home, it takes you a little longer to remember how to say certain expressions or words in your native language, Dominguez said.

However, this does not mean you have completely forgotten these native words. Rather, it just takes a bit longer for your brain to retrieve them, Dominguez noted. It's like your brain has to sort through a filing cabinet of two different vocabularies. But once you fully reimmerse yourself in the native language — in this scenario, by moving back home — you'll get quicker at doing this, Dominguez said.

An area of language that is slightly more resistant to being forgotten than vocabulary is grammar, she added.

For example, in a 2023 study in The Language Learning Journal, Dominguez and colleagues found that Spanish native speakers who spoke English as a second language did not change the way that they used the present tense in Spanish, which differs from that in English, after more than 15 years living in the U.K.

In Spanish, the present tense can have two meanings: to denote a regular action such as "I often run in the mornings" and to depict an action taking place at the time of speaking, for instance "I sing in the shower," Dominguez said. Contrarily in English, for this latter action you'd have to say "I am singing in the shower."

Research also suggests that a similar principle applies to forgetting a second language that you've lost touch with, which is conditional upon how much you originally learned and how long you learned it for. In fact, you may surprise yourself with how much you remember once you get back to it, Antonella Sorace, a professor of developmental linguistics at the University of Edinburgh in the U.K., told Live Science.

"Consciously, we may feel that we've forgotten everything — our brain knows better," she added.

Conversely, people with conditions such as dementia who are bilingual may be more likely to confuse languages and revert back to using only their native language. This latter phenomenon is known as language reversion and it can happen even after a lifetime of using both languages.