Although highly proficient bilinguals (or polyglots) comprehend and produce speech and writing without apparent difficulty, the higher-order mental mechanisms that are employed for expressing words in just the intended language take additional time and executive control. The results from several translation studies -in which reaction times, errors, and cross-language intrusions were analyzed under various experimental conditions- suggest that planning and supplementary mental effort are necessary at more than one stage in the linguistic hierarchy (namely-- conceptual, lexical, sublexlical, phonetic, or orthographic levels) to avoid dysfluencies and involuntary language switches.
This research addresses larger issues referring to how multiple languages are organized in the linguistic architecture, in what circumstances they interact with each other, and how the cognitive system accommodates them to ensure smooth and accurate expression. It has general implications for current models of language processing, as well as particular implications for language teaching and learning.