Sense of agency over speech and proneness to auditory hallucinations: The reality-monitoring paradigm

This study investigated the effects of imagining speaking aloud, sensorimotor feedback, and auditory feedback on respondents' reports of having spoken aloud and examined the relationship between responses to "spoken aloud" in the reality-monitoring task and the sense of agency over speech. After speaking aloud, lip-synching, or imagining speaking, participants were asked whether each word had actually been spoken. The number of endorsements of "spoken aloud" was higher for words spoken aloud than for those lip-synched and higher for words lip-synched than for those imagined as having been spoken aloud. When participants were prevented by white noise from receiving auditory feedback, the discriminability of words spoken aloud decreased, and when auditory feedback was altered, reports of having spoken aloud decreased even though participants had actually done so. It was also found that those who have had auditory hallucination-like experiences were less able than were those without such experiences to discriminate the words spoken aloud, suggesting that endorsements of having "spoken aloud" in the reality-monitoring task reflected a sense of agency over speech. These results were explained in terms of the source-monitoring framework, and we proposed a revised forward model of speech in order to investigate auditory hallucinations.