Do native speakers always outperform second-language (L2) learners in terms of speech processing accuracy Surprisingly, the answer to this seemingly obvious question is no according to the study reported here. Indeed, native speakers sometimes make more errors than learners in interpreting their own first-language (L1) speech. In this competition experiment of the double-object active and transitive causative sentence processing strategies, six native Japanese speakers and nine English-speaking learners of Japanese participated. The participants were required to identify the agents of the main lexical verb ("doers") of a series of Japanese sentences, each consisting of one verb and three noun phrases, in which word order and case-marking cues either competed or were consistent with each other. In the first (pretest) and last (posttest) parts of the study, participants received no feedback about the accuracy of their responses, whereas in the middle part they received immediate feedback. The stimulus sentences were such that a listener could determine the semantic role of noun phrases (actor, causer, or recipient) only by taking into consideration both the case markers and the verb's voice (active vs. causative). Learners of Japanese as a second language (JFLs) demonstrated an evident word order bias. Native Japanese speakers also made surprisingly numerous errors, by imposing the canonical case-marker sequence in reconstructing noncanonical sentences. Indeed some of the native Japanese revealed an even stronger word order bias than the learners, and they committed more errors than learners in interpreting noncanonical word order sentences. The results are explained in terms of the working memory constraint. Directions of further research are discussed.
