This study puts the usage-based assumption that our linguistic knowledge is based on usage to the test. To do so, we explore individual variation in speakers’ language use as established based on corpus data – both in terms of frequency of use and productivity of use – and link this variation to the same participants’ responses in an experimental judgment task. The empirical focus is on transfer by native German speakers living in the Netherlands, who oftentimes experience transfer from their (...) second language Dutch to their native language German regarding the placement of prepositional phrases. The analyses show a large amount of variation in both the corpus and experimental data with a strong link across data types: individual speakers’ usage – but not the usage by other speakers – is a significant predictor for the speakers’ judgments. These results strongly suggest that, in line with a usage-based approach, variation between speakers in experimental tasks is linked to their variation in usage. At the same time, such usage-based predictions do not explain all of the variation, suggesting that other individual factors are also at play in such experimental tasks. (shrink)