Verbal Response Inhibition and Stuttering in Adults

Abstract

Many adults who stutter (AWS) attempt to modify or suppress their stuttered speech daily. The ability to effectively suppress motoric behavior after initiation relies on executive functions such as inhibition – specifically verbal inhibition – a challenging task regardless of clinical status. Minimal published data are available about verbal inhibition in non-stuttering adults, and no data are available for AWS. Researchers have reported slower inhibition for AWS during manual tasks, but inconsistent relationships have been found between manual and verbal inhibition. It is often presumed that inhibition differences in AWS, if detected, would be associated with greater difficulties suppressing the motor characteristics of stuttering. However, data from adults who do not stutter (AWNS) suggest either faster or slower inhibition during manual tasks reflect negative affect – a characteristic not unfamiliar to AWS irrespective of severity. Thirty-four adults (17 AWNS, 17 AWS) completed manual and verbal stop-signal tasks. AWS were assessed for stuttering severity (Stuttering Severity Instrument; Riley, 2009) and experience with stuttering (Overall Assessment of the Speaker’s Experience with Stuttering; Yaruss & Quesal, 2010). The manual task required participants to respond to left/right arrows. The verbal tasks required participants to name two letters (“T”, “D”), two images (“bucket”, “castle”), or 12 images (e.g., “parrot”, “towel”) upon visual presentation. Participants attempted to suppress verbal responses post-presentation if stimuli changed color. Results indicate no correlation between manual and verbal inhibition for either group. Generalized linear mixed model analyses suggested no significant group differences, but did detect a significant effect from task. Overt stuttering severity was not found to be predictive of manual or verbal inhibition. Negative experiences with stuttering and severity of stuttering did not predict manual inhibition. However, experience with stuttering significantly predicted verbal inhibition. Increasingly severe scores on Reactions to Stuttering were related to faster verbal inhibition, whereas increasingly severe scores on General Information were related to slowed verbal inhibition. Although results contradicted expectations regarding the role of inhibition in stuttering, findings were in line with previous research relating affect to inhibition. Based on these findings, it is possible that verbal inhibition may be related to experience with stuttering.