Mechanism of implicit causality in L2 comprehension: Testing the empty-slot theory through coreference and coherence biases

This study investigated how implicit causality (IC) bias occurs in second language (L2) comprehension by testing the empty-slot theory’s core assumption: IC coreference bias emerges as an epiphenomenon of explanatory coherence bias. A story-continuation experiment compared Japanese learners of English and native English speakers in contexts where explanations were explicitly signaled (with because ) or left implicit (full-stop condition). When explanations were expected from IC verbs (coherence bias), IC influenced coreference (coreference bias) as strongly as in the because condition, supporting the central claim of the empty-slot theory. However, L2 learners showed significantly reduced coherence bias compared to native speakers, particularly for verbs whose lexical representations were underspecified or specified differently from native speakers. Consequently, they exhibited non-native-like coreference bias for IC verbs of lower lexical quality, specifically in the full-stop condition. These findings suggest that the cognitive mechanism of IC bias is qualitatively similar across first language (L1) and second language (L2) comprehension, evidencing the coherence-coreference link in the L2 context. At the same time, the magnitude of coreference and coherence biases is quantitatively weaker among learners than native speakers, especially when their lexical representations are less detailed or differently specified. This study extends the empty-slot theory to L2 discourse processing and identifies conditions under which L2 IC-based expectations are attenuated.