Crystallized and Fluid Cognition in Adults Who Stutter

Purpose: There is a long-standing perception that individuals who stutter are less intelligent, with the disfluencies unique to stuttered speech often assumed to be the overt reflection of lower intelligence, despite no supporting evidence. The purpose of the present study was to explore the validity of this assumption by examining the cognitive abilities of adults who stutter compared to the general population using the NIH Toolbox (C) Cognition Battery (NIHTB-CB). Method: Sixty-three adults who stutter completed the NIHTB-CB, which includes seven standardized measures assessing crystallized cognition (Picture Vocabulary, Oral Reading) and fluid cognition (List Sorting Memory Test, Pattern Comparison Processing Speed Test, Flanker Inhibitory Control Test, Dimensional Change Card Sort Test, Picture Sequence Memory Test). The NIHTB-CB generates t-scores adjusted for demographic variables based on a large sample of neurotypical adults. Results: Composite scores of overall cognition for adults who stutter were not statistically equivalent, rather, their scores were higher than the general population. Higher scores were driven by crystallized cognition, with significantly higher scores on Oral Reading subscale. Conclusions: Present findings demonstrate that adults who stutter possess cognitive skills that are comparable to or potentially higher, than the general population. These results challenge the misconception that stuttering reflects diminished intelligence and offer evidence to mitigate stereotype threat.