The investigators will examine the acute effects of stimulant medication on executive functioning. The rationale for the proposed study is to examine the efficacy of stimulants for college students with ADHD and help prevent stimulant misuse among college students without ADHD. The working hypothesis is that stimulants, compared to baseline and placebo conditions, will improve executive functioning for college students with ADHD but not for college students without ADHD. 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. Follow-up analyses will include paired comparisons. Expected outcomes are to confirm these hypotheses and demonstrate the need for further study of stimulants. If confirmed, the results will provide pilot data for a larger NIH grant proposal aimed at further examining the acute effects of stimulants (i.e., improved cognitive functioning with stimulants) and comparing them to the acute effects of physical exercise (i.e., improved cognitive functioning immediately after exercise). The investigators expect this outcome to have an important positive impact because it can help support stimulant medication as an effective treatment for college students with ADHD (DuPaul et al., 2012). Additionally, demonstration that stimulants do not improve executive functioning for college students without ADHD can be used to help prevent and discourage stimulant misuse and diversion on college campuses (Hartung et al., 2013).