Beyond word count: a pilot study of the verbal fluency task in chronic mild traumatic brain injury

Background To examine the clustering and switching behaviours, beyond total word count, as indicators of subtle executive dysfunction in individuals with and without a history of mild traumatic brain injury (mTBI), and to determine whether subcomponent analyses reveal cognitive inefficiencies overlooked by standard assessments. Methods Thirty-five university students (mTBI = 9; controls = 26) aged 18–24 years completed phonemic (FAS) and semantic (animal naming) verbal fluency tasks. Total correct responses, mean cluster size and number of switches were analysed. Results Compared with controls, individuals with mTBI produced fewer ‘S’ words (z = 2.66, P = 0.007, r = 0.45) and semantic switches (z = 2.45, P = 0.015, r = 0.41). Both groups were significantly different in semantic and phonemic clusters (mTBI: z = 2.22, P = 0.026, r = 0.74; controls: z = 3.51; P < 0.001, r = 0.69). No group differences were observed for phonemic switching. Findings indicate subtle reductions in cognitive flexibility and verbal productivity in individuals with chronic mTBI. Conclusions Clustering and switching analyses in verbal fluency tasks may detect subtle, executive deficits in individuals with chronic mTBI that are not captured by total word count alone. These findings support the feasibility of subcomponent verbal fluency measures as sensitive tools for long-term mTBI assessment and monitoring.