Vocabulary Retention In Adult Language Learners

What can we learn and implement from neuroscience to support long-term vocabulary retention in adult language learners?

Brain and Language

Neuroscience focuses on how different regions of the brain work and impact behavior and cognitive functions. Neurological processes and brain development data can provide insights into how students learn best, so that teaching and learning methodologies can be adapted to enable each student to achieve their full potential based on their individual capabilities (Goswami, 2006; University of Delaware, 2019).

For adult language learners specifically, difficulties arise very early on in their learning journey, when they are faced with grammar concepts and a lot of new vocabulary to remember while trying to practice speaking (including pronunciation). From a neuroscience perspective, it is important to first understand that Broca’s area and Wernicke’s area are two vital areas involved in processing language. Broca’s area is dedicated to speech production, while Wernicke’s area is related to vocabulary retention and language comprehension. With the help of the angular gyrus (processing language and memory), the insular cortex (involved with context, perception, and understanding), and the basal ganglia (processing the emotional content of language and the meaning of others), Wernicke’s area attaches the meaning to word sounds and shapes, and incorporates context into the interpretation (The Physiology of Human Language & Speech: The Brain & Nervous System, 2017). This complex region of the brain is key for adult language learners in their quest for language proficiency.

“This complex region of the brain is key for adult language learners in their quest for language proficiency

Using this knowledge as well as recent findings from brain research, this article aims at providing tools to support the creation of a positive and stimulating learning environment to enhance language learners’ long-term retention of new material, especially vocabulary. Four factors supporting vocabulary retention will be addressed, followed by five relevant tools that could be implemented in a language classroom.

Factors Supporting Vocabulary Retention

One of the key factors supporting efficient vocabulary retention in adult language learners is practice over time, as it helps consolidate new skills and knowledge (Genesee, 2000). As students practice repeating and reviewing new vocabulary, neurons become more efficient at making the same connections over and over again, which allow for easier retention and retrieval of that specific information (Pearce Stevens, 2014). To illustrate the point that practice and repetition are critical for language learning, a 2008 study asked a native English speaker to learn 15 new Arabic words a day for 20 days straight. After those 20 days, immediate and delayed vocabulary tests were provided to the language learner. The immediate vocabulary test indicated that almost all of the vocabulary items were retained by the learner. But it proved to be temporary, as the delayed vocabulary test showed a diminution in the number of words the learner could remember (Fitzpatrick, Al-Qarni, and Meara, 2008). Long-term retention of new vocabulary was unsuccessful in this case, possibly because of the lack of repetition and review of the newly acquired words.

A positive learning environment is also needed to improve vocabulary retention. Neuroimaging findings and analysis of neurotransmitters reveal that learners’ comfort levels can influence the transmission and the storage of newly acquired information (like vocabulary items) in the brain (Thanos et al., 1999). Studies have shown that emotion can deeply influence cognitive processes and impair students’ engagement, learning abilities and long-term retention of new material (Tyng et al., 2017). Therefore, it is recommended to ensure a positive, engaging, and stimulating learning environment to foster language proficiency achievements in adult language learners.

“[…] it is recommended to ensure a positive, engaging, and stimulating learning environment to foster language proficiency {…}”

Additionally, adult language learners’ acquisition of new vocabulary can be enhanced when used in complex real-world situations (Genesee, 2000). Indeed, language learners need a context-rich, meaningful environment to better remember new material, especially vocabulary. In a 2006 study, Pigada and Schmitt noticed that extensive reading can improve vocabulary acquisition, and potentially retention. The study assessed if 30 days of extensive reading could improve language learners’ knowledge of new words’ meaning and spelling. It demonstrated that vocabulary acquisition and retention vary based on the recurrence of the words within the text. The results showed that 65% of the newly acquired words were remembered by learners. Overall, extensive reading could be a relevant method to improve adult language learners’ acquisition and retention of new vocabulary.

Sleep is another factor supporting long-term retention of vocabulary. Brain studies showed that the brain is highly active during certain sleep stages, and that the reactivation of neural connections at night enables the consolidation of newly acquired information into long-term memory (Kelly, 2017). According to Penny Lewis, it is in the deepest kind of sleep that neurons fire in synchronous bursts, allowing new learning to pass into the neocortex to be stored more permanently (Campbell, 2014; Kelly, 2017).

Sleep is another factor supporting long-term retention of vocabulary

Tools Supporting Vocabulary Retention

As mentioned earlier, practice is key for adult language learners to retain new vocabulary. Therefore, frequent practice tests can enhance long-term retention of new vocabulary and limit test anxiety. Those practice tests do not have to be graded, they can be used either at the beginning or at the end of class time and can take the form of a pop quiz or a trivia quiz. Current tools such as Kahoot!, Microsoft Form, and Quizlet proved to be a relevant integration and usage of technology to support vocabulary retention in adult language learners.

The Spaced Repetition System (SRS) is another tool that can enhance long-term retention of new vocabulary. As early as the 1880s, German psychologist Hermann Ebbinghaus noticed that repetition was vital for learning, and that retention of such newly acquired learning was enhanced if it was repeated and if these repetitions were spaced out over time. Ebbinghaus (1913) also noticed that with time, students tend to forget what they learned. In his study, he noticed that without reinforcement or connections to prior knowledge, newly acquired knowledge was quickly forgotten; about 56 % was lost after one hour, 66 % after a day, and 75 % after six days (Ebbinghaus, 1913). To prevent forgetting new information (like vocabulary during language learning), spaced repetition allows students to strategically time vocabulary review to consolidate it into their long-term memory before it gets lost. This is an efficient method because it makes learning effortful, strengthening brain’s connections between the nerve cells (Custers, 2010). By spacing out vocabulary reviews, adult language learners are exercising these connections each time they review formerly-acquired vocabulary, which then allows for the long-term retention of this vocabulary (Larsen et al., 2009). Indeed, MIT neuroscientists explain that synaptic plasticity happens when neurons are frequently fired (Massachusetts Institute of Technology, 2015). Connections between neurons are then strengthened, allowing this new knowledge to stay in one’s memory for a longer period of time. As Terada (2017) explains, “repeatedly accessing a stored but fading memory rekindles the neural network that contains the memory and encodes it more deeply.”  For instance, a study led by Custers (2010) showed that medical students not using spaced repetition forgot about 50% of their science knowledge after two years.

Using texts and realistic images together is another great way to provide vocabulary input without using students’ native language

Using texts and realistic images together is another great way to provide vocabulary input without using students’ native language. Bui and McDaniel (2015) noted that it is easier for learners to remember what they read and saw together. Yoshii and Flaitz (2002) created a study with three groups of adult English learners having to retain vocabulary after reading a text online. The group tested immediately after the reading with both text and picture inputs outperformed the groups tested with text-only and picture-only inputs. Unfortunately, all three groups had declining scores on the delayed tests, showing that long-term retention of new words was not completely and successfully achieved. However, Hashemifardnia et al. (2018) concluded that picture books provided to Iranian English learners can lead to increased vocabulary acquisition and retention because of the close relation between the text and the corresponding image.

According to Sun (2017), adult language learners also retain vocabulary through group discussions and generative activities. For instance, adult language learners can create a graphic organizer and word clouds by associating words with their antonyms and synonyms, write their own definitions of the newly acquired vocabulary items, or use those new words in their own sentences. This is a relevant way for language learners to go beyond the traditional flashcard system and make connections between words by efficiently using their prior knowledge.

Another tool supporting adult language learners’ long-term retention of new vocabulary is the use of games, gamification, and technology (such as virtual reality). Simulation games have proved to be useful in improving long-term retention of new vocabulary (Franciosi et al., 2016). It also fosters language learners’ motivation by using levels, quests, badges, and rewards. As learners are engaged to move to the next level or to get the next badge, they are reviewing vocabulary regularly as they progress through the game.

To conclude, neuroscience can efficiently support adult language learners in their quest for long-term retention of newly acquired vocabulary, which is crucial to achieve language proficiency. Hopefully, new findings will emerge from brain research in the field of educational neuroscience, and those results could prove beneficial in selecting and developing new learning strategies for adult language learners.


Written by Aurore Bargat. Illustrated by Melis Cakar.
Edited by Zoe Dobler, Sean Noah and Desislava Nesheva.


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  • Aurore Bargat

    Aurore earned a B.A. and a M.A in Foreign Languages and Translation, and is now working as a foreign language teacher and a teacher trainer in California. Aurore is also an Ed.D student in Education Policy, Organization and Leadership at the University of Illinois at Urbana-Champaign, where she focuses on how neuroscience can benefit adult language learners in their quest for language proficiency.

Aurore Bargat

Aurore earned a B.A. and a M.A in Foreign Languages and Translation, and is now working as a foreign language teacher and a teacher trainer in California. Aurore is also an Ed.D student in Education Policy, Organization and Leadership at the University of Illinois at Urbana-Champaign, where she focuses on how neuroscience can benefit adult language learners in their quest for language proficiency.