The role of inhibition in the production of disfluencies.

Disfluency is a common occurrence in speech and is generally thought to be related to difficulty in the production system. One unexplored issue is the extent to which inhibition is required to prevent incorrect speech plans from being articulated. Therefore, we examined disfluency production in participants with attention-deficit/hyperactivity disorder (ADHD), which is linked to deficits in inhibitory function and response suppression (Nigg, 2001). Participants completed a sentence production task in which they were presented with two pictures and a verb and their task was to produce a sentence. If inhibition plays a role in preventing incorrect speech plans, we would expect ADHD participants to produce more repetition and repair disfluencies than would non-ADHD controls. The results showed that one subtype of ADHD (i.e., the combined) produced more repair disfluencies as task demands increased. We conclude that the production system relies on inhibitory control in order to prevent errors in language production.