The emergence of competing modules in bilingualism

Abstract

How does the brain manage to store and process multiple languages without encountering massive interference and transfer? Unless we believe that bilinguals live in two totally unconnected cognitive worlds, we would expect far more transfer than actually occurs. However, imaging and lesion studies have not provided consistent evidence for the strict neuronal separation predicted by the theory of modularity. We suggest that emergentist theory offers a promising alternative. It emphasizes the competitive interplay between multiple languages during childhood and by focusing on the dual action of competition and entrenchment, avoids the need to invoke a critical period to account for age of acquisition effects in second-language learning. This view instantiates the motto formulated by Elizabeth Bates that 'modules are made, not born.'

Figure 1

Snapshots of the DevLex model across stages of lexical development: Stage 1(upper left) 50 words; Stage 3(upper right) 150 words; Stage 5(lower left) 250 words; and Stage 10 (lower right) all 500 words. The self-organizing map separates the four major categories – Nouns, Verbs, Adjectives, and closed class words (CC) – clearly towards the final stage. (The labels for individual words are not legible because of the large number of words represented.)

Figure 2

Emergence of lexical representations in DevLex from Chinese–English bilingual input. Through self-organization, the network comes to separate the Chinese lexicon from the English lexicon, implicating distinct lexical representations for the two languages.

Figure I

(a) Parasitism: the Spanish ‘tortuga’ is a word associate of turtle without a direct link to meaning. (b) Later in learning, direct connections form between the L2 form‘tortuga’ and the meaning in L1. As L2 forms gain strength, they can compete with L1, and L1 can access L2 more readily.