This study investigated the hypothesis that in language contact situations, bilinguals develop strategies aimed at lightening the cognitive load of having to remember and use two different linguistic systems, resulting in changes in the secondary language. The study examined four specific strategies (simplification of grammatical categories and lexical oppositions; over-generalization of forms; development of periphrastic constructions either to achieve paradigmatic regularity or to replace less semantically transparent bound morphemes; direct and indirect transfer of forms from the superordinate language) and the patterns of diffusion of a number of changes in the linguistic system and their correlation with extralinguistic factors. Special attention is given to the issue of permeability at different stages of attrition or distance from the Spanish dominant norm. Data were gathered from several generations of Mexican-American bilinguals living in a mostly Hispanic area of Los Angeles (California) in 1983-1988. Survey questionnaires are appended. (Contains 209 references.) (MSE)