Filled pauses as cues to the complexity of upcoming phrases for native and non-native listeners

We examined whether filled pauses (FPs) affect listeners’ predictions about the complexity of upcoming phrases in Japanese. Studies of spontaneous speech corpora show that constituents tend to be longer or more complex when they are immediately preceded by FPs than when they are not. From this finding, we hypothesized that FPs cause listeners to expect that the speaker is going to refer to something that is likely to be expressed by a relatively long or complex constituent. In the experiments, participants listened to sentences describing both simple and compound shapes on a computer screen. Their task was to press a button as soon as they had identified the shape corresponding to the description. Phrases describing shapes were immediately preceded by a FP, a silent pause of the same duration, or no pause. We predicted that listeners’ response times to compound shapes would be shorter when there is a FP before phrases describing the shape than when there is no FP, because FPs are good cues to complex phrases, whereas response times to simple shapes would not be shorter with a preceding FP than without. The results of native Japanese and proficient non-native Chinese listeners agreed with the prediction and provided evidence to support the hypothesis. Response times of the least proficient non-native listeners were not affected by the existence of FPs, suggesting that the effects of FPs on non-native listeners depend on their language proficiency.