Iceberg Theory

[C. George Hunt]

Your student might be thinking of a pictorial representation of the
Common Underlying Proficiency model of bilingualism advanced by Cummins
(The Construct of Language Proficiency in Bilingual Education. In
Georgetown University Round Table on Languages and Linguistics
1980.Georgetown University Press.) This presents an alternative picture of
bilingual language development to the "two balloons" picture. The latter
envisgaes languages expanding at each other's expense in the limited
"space" of the bilingual brain, so that neither can be "fully learned".The
CUP model envisages the two languages as the twin peaks of a submerged
iceberg; the peaks are separate, but conjoined by, founded upon, and
communicating with, a common set of linguistic and cognitive principles.

Colin Baker summarises other picture theories of bilingualism in Key
Issues in Bilingualism and Bilingual Education, Multilingual Matters,
1988.