I’m chatting with my little cousin in Taiwan over FaceTime and telling her about a great movie I’d just watched. After providing what I thought was a pretty eloquent synopsis, I saw her giggle on the other end of the screen.
“What is it?” I asked, baffled.
“Did you know that you used English for all the most important keywords in that summary?”
“I did?”
My cousin nodded as she was trying to contain her laughter. I’m embarrassed and confused because I honestly didn’t even realize I’d slipped in some English words into our conversation.
By now I’ve accepted that these types of “incidents” are just part of my life. Sometimes I respond affirmatively to a question with 對—Chinese for “yes”—when having an otherwise all English conversation. Other times I struggle with remembering the Chinese equivalent of a perfectly simple English word.
Most of the time I have no problem switching back and forth between the two languages; in fact, I’m not even consciously cognizant of making this shift. But whenever I have a #byelingual moment, I wonder: how does the brain of a multilingual work? And what causes the little slip-ups that sometimes creep into our speech?
The Brain with Two Operating Systems

Not surprisingly, the brain needs to perform a complex set of maneuvers when a multilingual person wants to speak. All of the languages that a multilingual person knows are activated at the same time.
Think of it as a computer running more than one operating system like Mac and Windows in parallel.
For example, when a Chinese/English bilingual person sees a car, two words will pop up in their mind— the English word “car” as well as its Chinese counterpart “車”. Their brain has to decide which language to kick to the curb for the moment and which to use in a conversation.
This is a process scientists call “cognitive inhibition”. It’s what gives a multilingual person that seamless transition between languages.
Multilingual Blunders
As you can imagine, this mechanism isn’t 100% perfect.
When it fails, it manifests as a harmless (but still embarrassing) faux pas. This is exactly what happened when I accidentally described the movie with a mix of Chinese and English. My brain’s cognitive inhibition process suffered a glitch for whatever reason. The language that it was supposed to suppress ended up leaking into the conversation.
While there are some truly balanced bilinguals—those who have native fluency in both of the languages they know—most bilinguals probably are much more proficient in one language over the other.

Researchers have found that for these bilinguals, sometimes the proficiency of their dominant language takes a bit of a hit as they’re learning or improving the other language.
It turns out the brain is constantly trying to make both languages equally accessible by inhibiting the dominant language more. When this balancing act goes too far, a bilingual might find it hard to remember some words in their more dominant language.
This phenomenon is not just limited to vocabulary words, either. Some bilinguals will use the right word in the more dominant language they intend to use but will pronounce it using the wrong accent.
Embrace the Slip-Ups
It’s not all bad for multilinguals, of course! Quite the opposite, actually. No matter how you look at it, the social and cognitive benefits of being multilingual are undeniable.
Multilingual people are able to communicate and connect with more people, learning and sharing as they navigate the world. They are usually open-minded and willing to embrace new experiences and cultures. In the workplace, their language skills are pretty advantageous as the world becomes increasingly more global.
Cognitively, some research has shown that bilinguals have better executive control skills than monolinguals, likely due to the fact that their brains are constantly practicing these skills as they switch between languages.
The complex mechanisms required in successfully learning and using multiple languages keeps the brain agile. This heightened workout can help delay the onset of diseases like dementia.
Lastly, the brain of a multilingual person also shows denser grey matter, which is an area of the brain designed for processing information. Not bad, right?
Next time I have a #byelingual moment, I’ll just have to remind myself that the two operating systems of my brain are both hard at work, and I should cut them both a little slack.