Does learning a new language push the old ones aside?
Language learning is often viewed as an asset, an opportunity to broaden cultural and cognitive horizons. However, many polyglots report a peculiar challenge. As they acquire a new language, they sometimes struggle to recall words in the languages they had already mastered. This intriguing phenomenon raises a fundamental question: Is our brain designed to accumulate languages indefinitely, or does adding a new language disrupt access to those previously acquired?
A recent study by psycholinguistics researchers sheds light on the nuances of linguistic memory and the interference mechanisms that shape our ability to juggle multiple languages.
Inside the language lab: how our brain manages multiple tongues
A team from Radboud University sought to understand the effects of retroactive interference on linguistic memory, examining how learning a new language affects access to those learned earlier. Their study, published in the Quarterly Journal of Experimental Psychology in 2024, highlights a key cognitive phenomenon. When we learn a new language, our ability to retrieve words in previously acquired languages can be momentarily disrupted. This process, well-documented in cognitive psychology, manifests as increased difficulty recalling previously learned words. It suggests that the brain dynamically readjusts its linguistic connections as new knowledge is acquired, an idea that underscores core questions about brain plasticity and how multiple languages coexist in our memory.
The notion that newly acquired languages may obscure older ones is based on the principle of lexical competition. When a multilingual individual tries to retrieve a word, all the representations linked to that concept become simultaneously active, including those in other languages. Psycholinguistics research has thoroughly documented this phenomenon, potentially explaining why learning a new language can make it harder to access previously acquired languages.
The notion that newly acquired languages may obscure older ones is based on the principle of lexical competition.
How fresh linguistic knowledge challenges the familiar
In the study, researchers recruited 26 native Dutch speakers who were proficient in English as a second language (L2) but had never studied Spanish (L3). They first measured the participants’ English proficiency by asking them to name 46 objects in English. Next, half of these words were taught to them in Spanish. Finally, a test was administered to measure how well they could retrieve those words in English. Two experiments were conducted: one within a single session and another after a consolidation period between Spanish learning and the English test.
The findings showed that participants had more difficulty recalling English words after learning their Spanish equivalents, compared with words unaffected by this new language interference. Moreover, this effect did not diminish over time, suggesting that interference appears immediately after learning and does not require a consolidation phase to intensify. These observations support a linguistic competition effect, in which accessing one language temporarily inhibits another. Many bilinguals experience this daily, for instance, when a word in their native tongue eludes them after they have increased their use of another language. This interference seems especially pronounced among individuals who, by immersion, adopt a new language at the expense of their native one.
The question then is whether this interference is inevitable or if it can be alleviated by appropriate strategies. Although disconcerting, it is not insurmountable. Recent research suggests that regularly reactivating a language, through use or exposure, helps prevent its erosion and maintains its accessibility, keeping it from slipping away. This phenomenon, known as language attrition, refers to the gradual loss of a less frequently used language.
However, the challenge of accessing a once-familiar language does not signify an irreversible loss. Research in the neuroscience of language indicates that a person’s native tongue remains imprinted in the brain, even after years of non-use. A study conducted at McGill University and the Montreal Neurological Institute used brain imaging to show that adults of Korean origin, adopted at a young age by Dutch-speaking families and no longer exposed to Korean since childhood, still activated brain regions specific to the Korean language when they heard Korean sounds. Similarly, another study involving Chinese girls adopted by French-speaking families found that, although they had not used Chinese for several years, their brains responded differently to French compared to monolingual French speakers, revealing a persistent influence of their native language on how they process speech.
These findings suggest that linguistic attrition does not result from erasing memory traces but rather from reduced access to stored knowledge due to weaker activation of the relevant neural networks. This conclusion is supported by a study published in Royal Society Open Science, which examined Korean sound perception among Dutch adults. One group was composed of individuals born in Korea and adopted before the age of six by Dutch-speaking families, while the other group had never been exposed to Korean. The results revealed that, although the adoptees had stopped speaking their native language completely, they could still distinguish Korean phonetic contrasts with far greater accuracy than participants who had never been exposed to Korean.
These findings suggest that linguistic attrition does not result from erasing memory traces but rather from reduced access to stored knowledge due to weaker activation of the relevant neural networks.
These observations indicate that early language learning leaves a lasting memory trace, even if active use ceases entirely, and that later exposure can facilitate reacquisition. Consequently, a well-structured approach, including active engagement, carefully managed switching between languages, and frequent contextual reminders, can significantly mitigate attrition. Reading, listening to, or speaking a language regularly, especially in diverse and stimulating contexts, helps maintain it and preserve fluency.
On top of that, sleep, a mysterious catalyst for memory, plays a pivotal role in consolidating and stabilizing linguistic memories, making words less prone to forgetting. Nevertheless, not all languages face attrition in the same way. The environment in which a language is learned shapes its resilience; a language acquired in a rich, varied, and stimulating setting tends to be more deeply rooted and resistant to interference.
Rather than serving as a battleground where languages compete for mental space, our brain appears to dynamically adjust their interconnections, moving among them with remarkable plasticity. Although acquiring a new language may temporarily hinder access to previously learned languages, those earlier languages do not vanish. They remain deeply embedded in neural circuits and can be reactivated through renewed exposure or targeted stimulation. Instead of representing a straightforward erasure, language attrition reflects a dynamic reorganization of cognitive priorities based on an individual’s communicative needs. Consequently, cerebral plasticity plays a crucial role in both retaining languages and facilitating their eventual recovery, underscoring the notion that the native language serves as a durable linguistic anchor, even in the face of prolonged disuse.
These findings highlight that our brain does not simply store information in a rigid manner; it organizes this information in interconnected networks, where each new link can reshape access to existing knowledge. Rather than signifying an irreversible loss, interference underscores the dynamic nature of language learning, shaped by interactions between languages that can be both challenging and enriching. The ease with which a multilingual individual switches from one language to another depends on multiple factors, including usage, frequency of activation, and strategies to keep each linguistic repertoire active.
Human memory is not a vault where intact memories accumulate passively, but rather a living system in perpetual adaptation. Thus, learning a new language does not erase previous ones; instead, it reorganizes how we access them. This process is fluid, occasionally chaotic, and always revealing of the fascinating flexibility of human cognition.
References
Mickan, A., Slesareva, E., McQueen, J. M., & Lemhöfer, K. (2024). New in, old out: Does learning a new language make you forget previously learned foreign languages? Quarterly Journal of Experimental Psychology, 77(3), 530–550.
Pierce, L. J., Chen, J. K., Delcenserie, A., Genesee, F., & Klein, D. (2015). Past experience shapes ongoing neural patterns for language. Nature Communications, 6, 10073.
