Threshold Hypothesis
The Threshold Hypothesis, proposed by Jim Cummins (1976), states that a minimum level of proficiency in both languages must be attained before bilingualism can have positive cognitive effects. Below this threshold, bilingualism may confer no advantage and may even be associated with cognitive disadvantages — particularly when L1 development is interrupted before academic literacy is established.
Two Thresholds
Cummins (1976) identified two threshold levels, creating three zones:
| Zone | Proficiency level | Predicted cognitive effect |
|---|---|---|
| Below lower threshold | Low proficiency in both L1 and L2 | Possible negative cognitive effects |
| Between thresholds | Adequate proficiency in one language but not both | Neither significant advantages nor disadvantages |
| Above upper threshold | High proficiency in both languages | Positive cognitive effects (enhanced metalinguistic awareness, cognitive flexibility) |
The hypothesis proposes that the cognitive advantages associated with bilingualism — such as greater metalinguistic awareness, cognitive flexibility, and divergent thinking — only emerge when learners have crossed the upper threshold in both languages.
Theoretical Context
The Threshold Hypothesis was Cummins' response to contradictory findings in bilingualism research. Early studies (e.g., Saer, 1923) found bilingualism associated with lower IQ scores. Later studies (e.g., Peal & Lambert, 1962) found bilingual advantages. Cummins proposed that the contradiction could be resolved by considering the level of bilingual proficiency: studies finding negative effects had tested children with low proficiency in both languages (subtractive bilingualism), while studies finding positive effects had tested children with high proficiency in both (additive bilingualism).
Connection to the Interdependence Hypothesis
The Threshold Hypothesis works in tandem with the Interdependence Hypothesis. If academic skills transfer across languages (Interdependence), then interrupting L1 development before the threshold is reached undermines the cognitive foundation needed for both L1 and L2 academic success. This is the theoretical basis for supporting L1 maintenance in bilingual education rather than early L2 submersion.
Together, these hypotheses form Cummins' argument against subtractive bilingual education: if children are moved into L2-medium instruction before their L1 has reached the threshold level of CALP, they risk remaining below the threshold in both languages — a situation sometimes called semilingualism (though this term is now considered problematic and largely avoided in the literature; see MacSwan, 2000).
Criticisms
- Vagueness — the hypothesis does not specify what the threshold level is or how to measure it. This makes the hypothesis difficult to test or falsify.
- The semilingualism debate — critics (MacSwan, 2000) argue that the concept of being below threshold in both languages rests on deficit-based assumptions about bilingual speakers and has been used to pathologise minority language communities.
- Variability — Cummins acknowledged that the threshold likely varies by task, context, and cognitive domain, which weakens the hypothesis's predictive power.
- Confounding variables — studies linking low bilingual proficiency with poor cognitive outcomes often involve children from disadvantaged socioeconomic backgrounds, making it difficult to separate linguistic from socioeconomic effects.
Implications
Despite criticisms, the Threshold Hypothesis has had lasting influence on bilingual education policy:
- It provides theoretical justification for maintaining and developing L1 literacy alongside L2
- It warns against premature submersion in L2 without adequate L1 foundation
- It supports the design of bilingual programmes that aim for high proficiency in both languages (additive bilingualism) rather than replacement of L1 by L2 (subtractive bilingualism)