Using an experimental approach, project C05 will assess the acquisition of the specialist language of linguistics and the effect of this late development on the intra-individual register flexibility of students enrolled in bachelor programs for primary school teachers of German. A series of experiments are planned to elicit explanations of linguistic issues. The approach will allow controlling for non-linguistic factors of individual variation and deepen our understanding of how language users choose among register variants. The proposed investigation thus serves as a window onto the development of individual register flexibility in its relation to metalinguistic awareness during early adulthood. Further, it allows inferences about the effects of cognitive and educational factors on the range of inter-individual variability in communicative situations requiring specialized linguistic knowledge.