Developmental stuttering is a multifactorial, neurodevelopmental disorder that usually appears between the ages of 2 and 4 years and persists in 20–40% of children who start stuttering. The lifespan prevalence is around 0.8% and the lifetime incidence in the general population is 8%. Living with stuttering may negatively affect not only an individual’s communicative ability but also their overall quality of life. Recent theoretical models and research findings speculate that there is a link between inhibitory control (IC) and cognitive flexibility (CF) and the onset, development, and/or persistence of stuttering. Previous studies with children who stutter (CWS) and children who do not stutter (CWNS) have only focused on whether there are IC/CF differences between the two groups and have included either younger (3–6yrs) or older children (6–12yrs); these investigations were conducted with a variety of measures and the findings are inconsistent.

This thesis aimed to examine IC and CF in CWS and CWNS between the ages of 4 to 9 years and comparisons were made between younger and older subgroups. This study was the first to use visual computer tasks to examine IC and CF in a combined manner in these two groups. Additionally, the link between IC, CF, and speech disfluencies was studied by investigating possible associations between the results from the experimental paradigm and the number of disfluencies produced in speech samples based on story retelling and spontaneous conversation.

The results showed that under IC and CF task-conditions (a) CWS slow down more compared to age- and gender-matched CWNS, (b) lower IC and CF performance was associated with increased production of stuttering-like disfluencies (SLDs) in CWS, and (c) older CWS (7–9yrs) were slower and made more errors, while younger (4–6yrs) had comparable results to CWNS.

Our findings provide further support for previous claims of weaknesses in IC and CF in CWS as well as for a distinct role of IC and CF in the production of SLDs and the development and/or persistence of stuttering.