In learning a second language, a minimum threshold level of proficiency must be reached in that language before the learner can benefit from the use of the language as a medium of instruction in school, to avoid the negative effects of bilingualism. A second threshold is the level that must be reached for the positive effects of bilingualism to manifest themselves.
First and second language learning are dependent on each other. An increase in cognitive or linguistic capacity in one language enhances the development of similar capacities in the other. Second language learners who develop more cognitive or literacy skills in the first language will manifest the skills more rapidly in the second language.
Excerpt From an interview with Jim Cummins, University of Toronto:
People get the Threshold Hypothesis1 and the Interdependence Hypothesis2 mixed up. They say children have to reach a certain level of ability in their first language before we introduce them to English. That has been translated in some bilingual programs as saying, “Well, we’ve got to keep children away from English.” Nothing could be further from the truth. What the threshold idea is saying is “We’ve got to make children vibrantly bilingual. We’ve got to get them developing both languages.” If we do it properly, both languages will reinforce each other.
The Threshold Hypothesis only focused on explaining the results of studies that have looked at the effects of bilingualism on children’s development. The interdependence hypothesis looks at the relationships across languages. The implication I would see in those hypotheses is that we certainly want to develop students' first language and second language as strongly as possible. We don’t need to be afraid of English. We don’t need to delay the introduction of English. We should look at ways of increasing children’s intention in relation to language, focusing them on language, and getting them to play with language, getting them to explore language. We know that bilingual children tend to do it simultaneously. Imagine what they could achieve if we were to build that language-awareness development into our classrooms and get children, for example, Spanish-English bilingual children, looking at cognates (words that have the same root) in the two languages. Many of the most difficult words in English are based on Greek and Latin. A lot of those have cognates in Spanish. The most difficult words in English are words that many Spanish-speaking students have in their internal database in their heads. We’ve got to use (in a bilingual program or an English-only program) the knowledge of the first language that children have as a resource for learning English.
Cummins, J. (Interviewee). (March 1998). TELL Program Videotaped Interviews, Stamford, CN. Annela Teemant, Producer. Provo, UT: Brigham Young University
Adapted with permission from:
Teemant, A. & Pinnegar, S. (2007). Understanding Langauge Acquisition Instructional Guide. Brigham Young University-Public School Partnership.