Disfluencies reflect a...hm... competition between response options: evidence from a drift diffusion analysis

Disfluency can occur when a speaker faces difficulty in language production, but also as a strategy to stall for time and create an illusion of continuity in speech. To better understand the origin of disfluency, the current study used a drift diffusion model (DDM) in a context of semantic competition. We developed a speeded version of the picture–word interference paradigm, in which participants name pictures while ignoring distractor words. We applied the DDM approach to data from related vs. unrelated distractors but also from fluent vs. disfluent answers (e.g. “apple” vs. “hm...a-apple”). All results were mapped onto the drift rate parameter. Unrelated distractor words resulted in a higher drift rate compared to semantic distractors, and fluent answers resulted in a higher drift rate compared to disfluent answers. Results suggest that picture-word interference taps into the process of spreading activation through the lexical-semantic system. Similarly, disfluency reflects competition between response options, and is not a strategy from the speaker to stall for time to accurately name the picture.