Anti-zero pronominalization: when Japanese speakers overtly express omissible topic phrases

In this paper, we focus on cases where Japanese speakers overtly express a topic phrase that could have been omitted. We call this phenomenon anti-zero-pronominalization and hypothesize that this helps speakers gain time for planning a following utterance; anti-zero-pronominalization is another option to deal with cognitive load at the beginning of an utterance in addition to fillers and other speech disfluencies. Based on a quantitative analysis of a corpus of spontaneous Japanese dialogs, we investigate the difference between overt topic NPs and zero-pronouns. We show that i) the utterance is more complex when the topic is expressed as an overt NP than when it is expressed as a zero-pronoun; ii) turn-initial items such as fillers are produced less frequently when overt NPs appear than when zero-pronouns appear; and iii) the utterance becomes more complex when the last mora of the topic is more prolonged.