This article presents the results of experimental data on language production and comprehension. These show that adult learners of Dutch as an additional language, with different language backgrounds, and a L2 proficiency below level A2 (Waystage) of the Common European Framework of Reference for Languages (CEFR; Council of Europe, 2001), use dummy auxiliaries as a structural device and interpret them as semantically vacuous. Proficiency level in the target language, more than language background, seems to determine the occurrence of dummy auxiliaries, and also which dummy auxiliary is used. Participants at a lower level of language acquisition use both dummy auxiliaries "zijn" ("be") and "gaan" ("go"), whereas more advanced learners continue using predominantly dummy auxiliary "gaan." These findings suggest that both dummy auxiliaries have a trigger function in setting the step from nonfinite utterances, to utterances with dummy auxiliaries carrying morphological information, and finally to utterances in which the morphological information is carried by the finite verb.