ABSTRACT The present study examined why speakers of languages with flexible word orders are more likely to use syntactically complex non-basic word orders when they provide discourse-given information earlier in sentences. This may be because they are more efficient for speakers to produce (the Speaker Economy Hypothesis). Alternatively, speakers may produce them to help listeners understand sentences more efficiently (the Listener Economy Hypothesis), given that previous studies showed that the processing of non-basic word orders was facilitated when the felicitous context was provided (i.e. a displaced object refers to discourse-given information). We addressed this issue by conducting a picture-description experiment, in which participants uttered sentences with syntactically basic Subject-Object-Verb (SOV) or non-basic Object-Subject-Verb (OSV) in felicitous or infelicitous contexts while cognitive load was tracked using pupillometry and functional near-infrared spectroscopy. The results showed that the felicitous context facilitated the filler-gap dependency formation of OSVs in production, supporting the Speaker Economy Hypothesis.