Does training working memory or inhibitory control produce far-transfer improvements in set shifting for children with ADHD? A randomized controlled trial.

Children with ADHD show impairments in set shifting task performance. However, the limited available evidence suggests that directly training shifting may not improve shifting performance in this population. We hypothesized that this incongruence may be because impairments exhibited by children with ADHD during shifting tasks are due to deficits in other executive functions, as shifting tasks also engage children's working memory and/or inhibitory control abilities. This randomized controlled trial examined the extent to which neurocognitive training of working memory vs. inhibitory control can produce downstream (far-transfer) improvements in set shifting task performance. Children with ADHD ages 8-12 ( = 10.41, = 1.46; 12 girls; 74% White/Non-Hispanic) were randomized to either central executive training (CET; n = 25) or inhibitory control training (ICT; = 29), two next-generation digital therapeutics previously shown to improve their intended neurocognitive targets. Two criterion set shifting tests were administered at pre- and post-treatment. Results indicated that ICT was superior to CET for improving shifting accuracy (treatmentxtime: = .03, BF = 3.01, η = .09, = 0.63). ICT was also superior to CET for improving shifting speed, albeit on only one of the two outcome tasks ( = .02, BF = 4.53, η = .08, = 0.59). CET did not produce improvements in shifting speed or accuracy on either task ( > .52, BF > 2.62), but showed evidence for more general (non-shifting-specific) improvement in response times on one of the outcome tasks (shift trials, = 0.70; non-shift trials, = 0.68). Taken together, these findings confirm that inhibitory control is important for successful performance on shifting tests, and suggest that training inhibitory control may reflect a method for improving set shifting difficulties in children with ADHD.