Judgment of disfluency in people who stutter and people who do not stutter: results from magnitude estimation

Two experiments used a magnitude estimation paradigm to test whether perception of disfluency is a function of whether the speaker and the listener stutter or do not stutter. Utterances produced by people who stutter were judged as "less fluent," and, critically, this held for apparently fluent utterances as well as for utterances identified as containing disfluency. Additionally, people who stutter tended to perceive utterances as less fluent, independent of who produced these utterances. We argue that these findings are consistent with a view that articulatory differences between the speech of people who stutter and people who do not stutter lead to perceptually relevant vocal differences. We suggest that these differences are detected by the speech self-monitoring system (which uses speech perception) resulting in covert repairs. Our account therefore shares characteristics with the Covert Repair (Postma & Kolk, 1993) and Vicious Circle (Vasić & Wijnen, 2005) hypotheses. It differs from the Covert Repair hypothesis in that it no longer assumes an additional deficit at the phonological planning level. It differs from the Vicious Circle hypothesis in that it no longer attributes hypervigilant monitoring to unknown, external factors. Rather, the self-monitor becomes hypervigilant because the speaker is aware that his/her speech is habitually deviant, even when it is not, strictly speaking, disfluent.