This paper adopts a process-oriented approach to comparing EFL and ESL varieties and examines to what extent they are driven by general cognitive processes of language acquisition and production. A comparative corpus-study of lexical innovations in derivational morphology brings to light two general types of innovations: 1) interlingual, L1-based innovations, resulting from cross-linguistic influence, and 2) intralingual, L2-based innovations, resulting from various other processes. While the first type is virtually absent in ESL varieties, it is in the second type where similar types of innovations in EFL and ESL varieties can be observed. The paper argues that these innovations can be explained in terms of several underlying cognitive processes that serve to create and maximise morphological transparency and increase explicitness of form-meaning relations.