Robbeets received a Ph.D. in Comparative Linguistics from Leiden University, and also received a master's degree in Korean studies from Leiden University. She also holds a master's degree in Japanese studies from KU Leuven.
In 2017, Robbeets proposed that Japanese (and possibly Korean) originated as a hybrid language. She proposed that the ancestral home of the Turkic, Mongolic, and Tungusic languages was somewhere in northwestern Manchuria. A group of those proto-Altaic ("Transeurasian") speakers would have migrated south into the modern Liaoning province, where they would have been mostly assimilated by an agricultural community with an Austronesian-like language. The fusion of the two languages would have resulted in proto-Japanese and proto-Korean.[3][4]