Stimuli examples of each condition.

Previous studies conducted across multiple languages have found processing differences between patient-first and agent-first word orders. However, the results of these studies have been inconsistent as they do not identify a specific event-related potential (ERP) component as a unique correlate of thematic role processing. Furthermore, these studies generally confound word order with frequency, as patient-first structures tend to be infrequent in the languages that have been investigated. There is evidence that frequency of syntactic structure plays an important role in language processing. To address this potential confounding variable, we test Standard Indonesian, a language where passive structures occur with high frequency and are comparable in frequency to active structures. In Standard Indonesian, there is evidence from acquisition, corpus, and clinical data indicating that the use of passive is frequent. In the present study, 60 native speakers of Indonesian read 100 sentences (50 active and 50 passive) while EEG was recorded. Our findings reveal neural correlates of thematic role processing in the passive sentence condition – specifically, a positive shift corresponding to a P600 on the verb, and a more sustained positivity on the second noun phrase. These findings support existing evidence that sentences with a ‘non-default’ word order impose increased cognitive load, as reflected by ERPs, even when they occur with higher frequency in the language.