Inclusion Criteria:  For ADHD Cohort  Aged between 18 and 26 years at the start of the study Providing documentation of ADHD being clinically diagnosed by a psychologist, psychiatrist, or a neurologist 3) Taking their prescribed ADHD medication >5 days a week  4) Currently playing soccer (i.e., intercollegiate, intramural, club) 5) At least 5 years of soccer heading experience  For non-ADHD Cohort  Aged between 18 and 26 years at the start of the study Absence of prior or current clinical diagnoses of ADHD Absence of prior or current history of taking ADHD medication 4) Currently playing soccer (i.e., intercollegiate, intramural, club) 5) At least 5 years of soccer heading experience  Exclusion Criteria:  For both ADHD and non-ADHD Cohorts  Any head or neck injury in the year before the start of the study Current use of medications that trigger drowsiness Pregnancy Any history of neurological disorders and learning disability other than ADHD Metal implants in the head Implanted electro/magnetic devices (e.g. orthodontic braces, pacemakers, aneurysm clips)