Background: Impulsivity is acting 'without thinking.' Compulsivity is being overly inflexible. People vary in how impulsive or compulsive they are. Extreme versions of these behaviors play a role in mental disorders. Researchers want to study changes in the brain to learn more about these behaviors. Differences in genes may also play a role.

Objective: To learn about genetic \& brain features that explain why levels of impulsivity and compulsivity vary across people.

Eligibility: People ages 6 - 80

Design: Participants will be screened with a medical history and medical record review. Participants will talk about their mental and behavioral development. They may discuss topics like drug use and sexual activity. They will complete surveys about their compulsivity and impulsivity. Parents of child participants may also complete these surveys. Participants may take memory, attention, and thinking tests. They may give blood or saliva samples for gene studies and they may give blood to make induced pluripotent stem cells. Participants may have their face and irises photographs taken. Participants may have a magnetic resonance imaging scan. It will take pictures of their brain. The scanner is shaped like a cylinder. Participants will lie on a table that slides in and out of the scanner. A coil will be placed over their head. They will lie still, watch a movie, and play a game. Participants may ask family members to join the study. Researchers are particularly interested in recruiting twin pairs to the study. Participants under age 25 may repeat these tests every 1-2 years until they turn 25 or until the study ends. For those over age 25, participation will last less than 1 month.