The bilingual lexicon refers to the mental representation and organization of vocabulary from two (or more) languages within a single cognitive system, encompassing how words from each language are stored, how they relate to each other and to shared conceptual representations, and how they are selectively or jointly activated during comprehension and production. Understanding the bilingual lexicon is central to both theoretical psycholinguistics and applied second language acquisition research.

In-Depth Explanation

The bilingual lexicon is not two separate stores but a single integrated network where words from both languages are simultaneously active during processing. The Revised Hierarchical Model (Kroll & Stewart, 1994) proposed asymmetric connections — early L2 learners access meaning through L1 mediation, while advanced bilinguals build direct L2-to-concept links. BIA and BIA+ models extended this with connectionist architecture. The core implication: vocabulary learning should aim not just for translation knowledge but for rich, direct conceptual associations in L2.

Is There One Lexicon or Two?

A foundational question is whether bilinguals maintain two separate lexica (one per language) or a single integrated lexicon with language-tagged entries. The evidence overwhelmingly supports a single, integrated system: words from both languages are activated simultaneously during processing, even when only one language is being used.

Evidence includes:

• Cross-language priming: Translating “table” activates the L2 equivalent (e.g., mesa in Spanish) even in a task where Spanish is irrelevant
• Cross-language homograph effects: Words that look the same in two languages (e.g., gift = present in English, poison in German) create interference
• Cognate effects: Translation equivalents sharing form and meaning are processed faster than non-cognates
• Language non-selective lexical access: Presenting words in one language activates phonological neighbors in the other language

Theoretical Models

Revised Hierarchical Model (RHM; Kroll & Stewart, 1994)

The RHM proposes distinct representational levels for words (lexical level) and concepts (conceptual level), with asymmetric connections between L1 and L2:

• Strong direct connections from L2 words → L1 words (especially for less proficient bilinguals)
• Strong connections from L1 words → concepts
• Weaker direct connections from L2 words → concepts

Prediction: L2 learners initially access word meaning through L1 mediation; as proficiency increases, direct L2-to-concept links strengthen. This accounts for why less proficient bilinguals translate mentally when comprehending L2, while advanced bilinguals comprehend directly.

Bilingual Interactive Activation Model (BIA; Van Heuven et al., 1998)

Extended the interactive activation framework (from word recognition research) to bilingual contexts. Both languages exist in a single representational network, with all visually similar words (orthographic neighbors) activated in parallel regardless of language membership. A language node mechanism allows top-down inhibition to suppress the non-target language.

BIA+ (Dijkstra & Van Heuven, 2002)

Updated the BIA model to separate the identification system (non-selective activation, shared) from the task/decision system (where language goals and context apply). This cleanly predicted when language non-selectivity produces visible behavioral interference vs. not.

L1–L2 Asymmetries

Lexical Selection in Bilingual Production

During speech production in one language, words from both languages are simultaneously activated. Bilinguals must select the target-language word while suppressing competing L1 or L2 alternatives. The primary proposed mechanism is inhibitory control: the dominant language is actively suppressed to allow the weaker language to be selected. Evidence for this includes the language switch cost (slower production on language switch trials in bilingual experiments) and the counter-intuitive finding that bilinguals show stronger inhibition of the dominant L1 precisely when switching to it from a weaker L2.

Development of the Bilingual Lexicon

The bilingual lexicon is not static. As L2 proficiency increases:

1. Direct L2-to-concept connections strengthen (less L1 mediation)
2. Phonological representations for L2 words consolidate
3. The mental lexicon becomes more elaborated with collocational, morphological, and pragmatic associations
4. Susceptibility to cross-linguistic influence and tip-of-the-tongue states decreases

History

• 1980s — Field origins. Word recognition and spreading activation research establishes that both languages are co-active during bilingual processing.
• 1994 — Revised Hierarchical Model. Kroll and Stewart propose asymmetric L2→L1 vs. L1→concept connections, becoming the dominant theoretical framework for two decades.
• 1998–2002 — BIA and BIA+ models. Van Heuven and Dijkstra develop connectionist models; BIA+ separates language-non-selective identification from language-selective decision processes.
• 2000s — Inhibitory control emphasis. Albert Costa’s work on language selection and production-stage inhibition becomes influential.
• Contemporary — Real-time methods. Eye-tracking, ERP, and pupillometry reveal millisecond-precision dynamics of bilingual lexical activation.

Common Misconceptions

“Bilinguals keep their languages completely separate.”

Extensive evidence shows both languages are always active to some degree, even when only one is being used. Complete separation is not achievable or necessary.

“Bilinguals always think in one language.”

Language of thought is fluid and context-dependent. Many bilinguals operate conceptually without mediation through any specific language form for highly familiar concepts.

“Advanced bilinguals are equivalent to monolingual speakers.”

Even highly advanced bilinguals show measurable differences in lexical access speed and cross-language interference compared to matched monolinguals.

Criticisms

• RHM conceptual link assumption: Treats L2-to-concept links as uniformly weak; more recent work shows even early learners acquire direct conceptual mappings, especially for concrete nouns.
• European language bias: Both RHM and BIA models were primarily developed for European-language pairs and face challenges with typologically distant pairs (e.g., Chinese–English).
• Switch cost symmetry: The inhibitory control model predicts asymmetric switch costs, but some evidence shows symmetric costs, questioning the proposed inhibition mechanism.

Social Media Sentiment

Bilingual lexicon topics generate vibrant social media discussions, especially around code-switching, the experience of “thinking in L2,” and the frustration of L1 interference in production. Advanced learners celebrate milestone moments when they stop translating mentally — a subjective marker of the shift from L1-mediated to direct L2-concept access. Multilingual speakers often debate whether they have “different personalities” in each language, a claim that has some empirical basis in how cultural schemas are organized differently across languages.

Last updated: 2025-07

Practical Application

For L2 learners, the bilingual lexicon research translates into actionable guidance. The goal of vocabulary instruction is not merely knowing a translation equivalent, but building rich, direct conceptual associations in L2 — moving from L1-mediated access to direct access. This requires not just studying translation pairs but encountering words in rich, varied L2 contexts, in multiple modalities, and through active retrieval. Spaced repetition supports the development of direct L2-to-concept links by systematically recycling words in varied contexts across intervals optimized to consolidate both semantic and phonological form access.

Related Terms

• Psycholinguistics
• Mental Lexicon
• Lexical Access
• Word Recognition
• Spreading Activation
• Cross-Linguistic Influence
• Tip-of-the-Tongue
• Speech Production
• Spaced Repetition
• Second Language Acquisition

See Also

• Bilingualism: Language and Cognition (Cambridge journal)

Research / Sources

• Kroll, J. F., & Stewart, E. (1994). Category interference in translation and picture naming: Evidence for asymmetric connections between bilingual memory representations. Journal of Memory and Language, 33(2), 149–174.
  Summary: Proposes the Revised Hierarchical Model, demonstrating asymmetric translation times and providing the dominant theoretical framework for L1–L2 lexical organization.
• Dijkstra, T., & Van Heuven, W. J. B. (2002). The architecture of the bilingual word recognition system: From identification to decision. Bilingualism: Language and Cognition, 5(3), 175–197.
  Summary: Proposes BIA+, distinguishing language-non-selective identification from language-selective decision processes; clarifies when bilingual parallel activation produces observable interference.
• Kroll, J. F., Bobb, S. C., & Wodniecka, Z. (2006). Language selectivity is the exception, not the rule: Arguments against a fixed locus of language selection in bilingual speech. Bilingualism: Language and Cognition, 9(2), 119–135.
  Summary: Reviews evidence that both languages compete at the lexical level and inhibitory control operates at the decision stage; influential in grounding the inhibitory control model of bilingual language use.