Participants. The investigators will enroll 40 University of Wyoming (UW) and Laramie County Community College (LCCC) students including 20 with ADHD and 20 without ADHD (20 men, 20 women). Power analyses (G\*Power 3.1; Faul et al., 2007) indicated a sample of at least this size is needed to provide 80% power to detect medium effects. Participants will be recruited through several means including targeted email announcements, flyers, and SONA pre-screener data.

Full exclusion criteria can be found in the "Eligibility" section below. Most notably, participants must stratify as being low risk for stimulant medication use. A health history screening questionnaire and additional health items will be used to screen participants and responses will be reviewed and approved by a medical consultant.

All prospective participants will attend a baseline appointment to confirm eligibility including: (a) being at low risk for stimulant use contraindications and (b) meeting diagnostic threshold for ADHD. After confirming eligibility, participants will also complete baseline measures during the baseline appointment. After enrolling in the study, participants will be scheduled for two experimental appointments. The two experimental appointments will include: (a) Placebo pill and (b) Stimulant (Adderall IR 10mg). The ordering of experimental appointments will be counterbalanced. Experimental appointments will be scheduled in the mornings and on the same day of the week and same time of day. Participants will be asked to abstain from caffeine, alcohol, nicotine, and illicit drugs for 12 hours prior to their appointments. Participants will be administered either placebo or stimulant. After a 90-minute wait, participants will complete executive functioning measures. Physiological measures (e.g., heart rate and blood pressure) will be monitored at specific times throughout the appointment and a medical consultant will be available on call for any emergencies. Participants will also be sent a modified mood (i.e., Depression, Anxiety, and Stress Scale or DASS) and sleep (Pittsburgh Sleep Quality Index or PSQI) questionnaire the morning following all experimental appointments. The only difference between the two appointments is the administration of either placebo or stimulant.

Prior to analyses, all variables will be screened. Violations of statistical assumptions will be addressed through data transformations or nonparametric statistics. Improvements on executive functioning measures (e.g., CPT-IP, Spatial Span) will be examined through 2 (ADHD vs. non-ADHD) x 3 (Baseline, Placebo, Stimulant) repeated measures ANOVAs. When interactions are significant, paired samples t-tests will be used to evaluate group differences. When interaction effects fail to reach statistical significance, independent samples t-tests will be used to evaluate group differences. The magnitude of omnibus effects for repeated measures ANOVAs will be calculated using partial eta-squared (ηp2). Within-group effects (Cohen's d) and corresponding confidence intervals for within-group effect sizes will be standardized using the variability of baseline scores (Howell, 2011). Between-group effects will be calculated using Hedges g (Hedges, 1982).