This article investigates the role of second or non-native languages (L2) in the acquisition of an additional language (L3). It studies the impact of cross-linguistic influence on the placement of the adjective in the Noun Phrase. The analysis of oral data from learners of Spanish L3 shows that the position of adjectives departs from the canonical word order of both Spanish L3 and French L1, reflecting the word order that characterizes the other languages known by the speakers, English and German. This paper will attempt to identify the psycholinguistic factors underlying this phenomenon. Particular attention will be placed on the ‘foreign language effect,’ which can transform non-native languages into a default grammatical model for the processing of L3 linguistic input.