Are multiword frequency effects stronger in non-native than in native speakers?

This study investigated whether non-native English speakers showed a processing advantage for high-frequency multiword units (multiword frequency effects), and whether the effects differed between native and non-native speakers. Such a difference has been identified in relation to single-word processing. Native English speakers and intermediate learners of English with languages of different scripts (native speakers of Japanese and German) judged whether English multiword units were grammatical. A significant processing advantage was identified for both native and non-native participants. More importantly, the multiword frequency effects were stronger among non-native than native speakers. The discrepancy persisted even after including individual vocabulary knowledge as a predictor in the mixed-effect models. Furthermore, there was no significant different impact of the effects between two non-native groups, even though German participants responded quicker than Japanese participants. This indicates that the varying influence between L1 and L2 could be explained by within-language, not between-language, variables.