Case marking is the major cue to sentence interpretation in Japanese, whereas animacy and word order are much weaker. However, when subjects and their cases markers are omitted, Japanese honorific and humble verbs can provide information that compensates for the missing case role markers. This study examined the usage of honorific and humble verbs as cues to case role assignment by Japanese native speakers and second-language learners of Japanese. The results for native speakers replicated earlier findings regarding the predominant strength of case marking. However, when case marking was missing, native speakers relied more on honorific marking than word order. In these sentences, the processing that relied on the honorific cue was delayed by about 100 ms in comparison to processing that relied on the case-marking cue. Learners made extensive use of the honorific agreement cue, but their use of the cue was much less accurate than that of native speakers. In particular, they failed to systematically invoke the agreement cue when case marking was missing. Overall, the findings support the predictions of the model and extend its coverage to a new type of culturally determined cue.