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The percent high-effort selections among ADHD and non-ADHD groups after placebo (PLA, white bars) and methylphenidate (MPH, black bars). MPH had a greater effect in the ADHD group than the non-ADHD group (Group × Drug interaction effect, p = .001). Shown are the estimated marginal means (including age as a covariate of no interest). Error bars are S.E.M.
