Bilingualism

Bilingualism is the use of two languages by an individual or within a community. It is the most common human linguistic condition — monolingualism is the exception globally, not the norm.

Individual Bilingualism

Types

Type	Definition
Simultaneous	Two languages acquired from birth (bilingual first language acquisition)
Sequential/successive	L2 acquired after L1 is established (early or late)
Balanced	Equal proficiency in both languages — rare in practice
Dominant	Greater proficiency in one language; dominance shifts by domain and life stage
Receptive/passive	Can understand but not produce the second language

The Dominance Principle

Balanced bilingualism — equal facility in all domains in both languages — is an idealisation. In reality, bilinguals typically use each language in different domains (home, work, education, religion) and their proficiency varies accordingly. A Vietnamese-English bilingual may be dominant in Vietnamese for family topics but dominant in English for academic discourse.

Societal Bilingualism

A community or society where two languages are in regular use. This may involve:

• Official bilingualism — two languages have legal status (Canada: English/French; Singapore: English/Mandarin/Malay/Tamil)
• De facto bilingualism — widespread bilingual practice without official recognition
• Diglossia — two varieties serve complementary functions (High/Low)

Additive vs Subtractive Bilingualism

Lambert (1974) distinguished two outcomes:

• Additive bilingualism — L2 is added without loss of L1. Associated with positive cognitive and social outcomes.
• Subtractive bilingualism — L2 replaces L1, often because the L1 is devalued socially. Associated with cognitive disadvantage and identity loss. Common in immigrant and minority language contexts.

The distinction is critical for education policy: immersion programmes work additively when the L1 is socially strong (e.g., English speakers learning French in Canada) but may work subtractively when the L1 is already threatened (e.g., indigenous language speakers in English-medium schools).

Cognitive Effects

Research since Peal & Lambert (1962) has shown cognitive advantages for bilinguals:

• Enhanced metalinguistic awareness
• Better executive function (attention, inhibition, task-switching)
• Greater cognitive flexibility

However, the "bilingual advantage" in executive function has been debated, with some studies failing to replicate the effect (Paap & Greenberg 2013). The metalinguistic advantage is more robust.

Cummins (1979, 1984) proposed the threshold hypothesis — a minimum level of L2 proficiency is needed for cognitive benefits — and the interdependence hypothesis — academic skills transfer across languages. See BICS and CALP.

Relevance to ELT

• Most English learners worldwide are becoming bilingual or multilingual, not replacing their L1
• Teachers should promote additive bilingualism — valuing L1 as a resource, not an obstacle
• Code-Switching and Translanguaging are natural bilingual practices, not signs of deficiency
• Bilingual learners have Multi-competence — their linguistic system is qualitatively different from, not inferior to, a monolingual's
• Understanding bilingualism helps teachers interpret learner behaviour: code-switching, L1 influence, and domain-specific proficiency variation are all normal bilingual phenomena