Resumen

Abstract
In this paper we analyse the recurrent mistakes produced by primary-school Spanish-speaking children learning English in two tasks designed to research the acquisition of passive constructions and unaccusative verbs. The regularity and systematicity with which they occur and the directionality in terms of preference for a particular incorrect form (White, 2003) point to stages in their developing IL systems and reveal that the different subsystems of learners‘ IL grammar interact in the path until each structure is fully acquired.