In this study, we apply Gries and Deshors’s (2014) and Deshors and Gries’s (2016) MuPDAR(F) approach to explore the use of synonymous adjectives tärkeä (i.e. “important”) and keskeinen (i.e. “central”) in academic native and advanced learner Finnish, linking the phenomenon with the general assumptions of usage-based cognitive linguistics. This method confidently modelled the differences between using near-synonyms in native data and distinguished between native-like and non-native-like uses in learner data. Crucially, it differentiated between the contexts in which one synonym was clearly favoured and those in which either one was acceptable, in accordance with Gries and Deshors (2020). The results suggest that Finnish learners fairly coherently follow the tendencies of native speakers, but several variables differentiate their use of synonyms from the latter’s. We interpret the differences to reflect complexity- and prototypicality-related phenomena. On the one hand, learners use more common options more often. On the other, non-nativelike adjectives are used only in contexts that are structurally in the most prototypical and least complex form, suggesting that learners employ complexity-related structural alternations – e.g., non-prototypical grammatical subjects or degree modifiers – after lexical alternations.