Statistical learning and rhythmic ability in Attention-Deficit/Hyperactivity Disorder: Individual differences outweigh group effects

Speech segmentation is fundamental to language acquisition and supported by statistical learning (SL). Research on SL is inconclusive as to whether it can occur outside the scope of attention and whether SL is impaired in individuals with Attention-Deficit/Hyperactivity Disorder (ADHD). Furthermore, individual differences in SL are hypothesized to be influenced by other cognitive abilities such as musical rhythmic ability (RA) and phonological working memory (WM), which previous literature indicated may be impaired in ADHD. The current study investigated SL in participants diagnosed with ADHD (N = 41) and neurotypical (N = 118) peers, exposing them to an artificial language and assessing SL both during exposure using EEG-measures of neural entrainment, as well as behaviorally after exposure. Furthermore, we explored whether multiple tasks assessing RA and WM were related to SL ability, and how SL related to vocabulary size. Bayesian statistical evidence indicated absence of group differences on SL, RA, WM, and vocabulary. Instead, individual variability outweighed group effects. Combining the groups yielded anecdotal evidence for a positive correlation between SL and vocabulary size, but not between SL and RA or WM. These results suggest that SL operates comparably in our samples of neurotypical individuals and individuals with ADHD, and was not found to be related to tasks assessing RA or WM. Notably, our sample consisted of mostly female participants in both groups. Future studies may want to further examine gender differences in ADHD symptoms and take a dimensional approach to ADHD symptomatology in relation to individual differences in SL ability.