This study investigates the argument drop pattern of a Korean psych-predicate construction in different modalities: spoken, written, and messenger language. Previous studies showed that native Koreans tend to interpret the ambiguous psych-predicate construction John-i mwusewun ka po-a-yo as ‘John must be scared’ when a new topic begins but as ‘John must be scary’ when an existing topic continues. However, regardless of the topic status, second language speakers (L2ers) of Korean preferred the former interpretation, and heritage language speakers (HLers) the latter. The present study investigates whether the discrepant interpretation patterns stem from the types of input L2ers and HLers are exposed to. The National Institute of Korean Language’s Word Sense Tagged Corpus 2020 was used to find the patterns with which the arguments were dropped from the ambiguous construction in spoken, written, and messenger corpora, using sentences with the psych-predicate mwusep- for preliminary investigation. The results show that the stimulus was overtly realized much more frequently than the experiencer in all three modalities, and it was significantly more so in the written corpus. Implications are discussed in light of the relationship among input, proficiency, and language development. (Kunsan National University)