Zoe E. G. Greenwood¹, Paul Brancaleone², Bruce D. Bartholow³; ¹The University of Iowa 1, 2, 3

The present analyses aimed to characterize individual differences in sustained attention in adolescents via changes in behavioral performance and event-related potentials during a flanker task. Participants (Ps) were 313 adolescents and emerging adults (ages 14-19; M_age = 16.7; 66% female) recruited for an ongoing longitudinal study of alcohol use risk. Ps completed 300 trials of a standard arrowhead flanker task across three equal blocks while EEG was recorded. Ps were assigned to one of three post-hoc groups (ns = 104-105 each) based on change in reaction time (RT) across the task (Block 3 - Block 1): RT improvers, RT stable, and RT worseners. Analyses tested for group differences in changes in P3 amplitude, indexing attentional and motivational processing, and N2 amplitude, indexing conflict monitoring, across blocks. Mixed factorial ANOVAs and linear regressions were conducted in Jamovi and R, with Ps’ age and sex included as covariates. Flanker congruency effects in accuracy did not differ across the post-hoc groups, F(2, 298) = 0.197, p = .821. There was a significant Block x Group interaction for P3 amplitude, F(4, 556) = 2.43, p = .047, indicating P3 change varied across groups. Post hoc Tukey tests showed that from Block 1 to Block 3, RT worseners showed the largest decrease in P3 amplitude (mean difference = 1.74, p < .001), RT stable participants showed a smaller decrease (mean difference = 0.64, p = .038), and RT improvers showed no significant change (mean difference = 1.65, p = .207). There were no P3 latency effects between groups and no significant difference in N2 amplitude. These findings suggest that worsening performance over time on a cognitive control task reflects reduced sustained attention and task motivation. Larger decreases in P3 amplitude were observed among participants whose performance worsened, whereas conflict monitoring did not differ across groups.