1. Young adults who are exposed to 7-10 days of play of violent video games will show reduced activation in certain regions of the dorsolateral prefrontal cortex and anterior cingulate cortex.
2. Young adults who are exposed to 7-10 days of violent video games will show increased activation in regions of the amygdala.
3. Young adults who abstain from violent video games for a week, after 7-10 days of play of violent video games, will show increased activation of regions in the dorsolateral prefrontal cortex and anterior cingulate cortex and decreased activation of the amygdala, on pre-post fMRI and compared to young adults who continue to play violent video games.
4. Young adults who complete a computerized attention-training program after 7-10 days of violent video games will show increased activation of regions in the dorsolateral prefrontal cortex and anterior cingulate cortex and decreased activation of the amygdala, on pre-post fMRI and compared to young adults who continue to play violent video games.

After an initial screening visit (Visit 1) followed by a one-week period of monitoring their usual media habits, subjects will have a baseline functional magnetic resonance imaging (fMRI) scan (Visit 2). They will then be assigned in a 3:1 ratio to either one-week of violent video game play for 1-2 hours per day or no video game play for one week. Subjects will receive a second fMRI scan at the end of that week (Visit 3). Subjects who had played violent video games will then be assigned to one of three conditions (continued regular violent video game play, no video game play, or an intervention involving cognitive training of working memory) for one week, in order to investigate the persistence of any changes that are found after the first week of exposure. Subjects who had not played video games during the first week will continue to not play video games for the second week. Following that week, subjects will receive a third fMRI scan (Visit 4). One week after the third fMRI scan, subjects will have a final visit or phone call to check on the possibility of any issues with aggressive thoughts/feelings/behavior following the video game exposure in the study (Visit 5). Brain functioning will be measured using functional magnetic resonance imaging (fMRI) as the primary measurement methodology, with neuropsychological testing used as a secondary measurement methodology.

Inclusion Criteria:

1. Have K-BIT-2 Matrices IQ>70.
2. Must be 18-29 years old for the entire study.
3. Only males will participate in the study.
4. Must be judged by the investigator to be reliable and cooperative for clinic visits and procedures.
5. Must speak English, be proficient in spoken and written English, and have an educational level and understanding of English required to complete all tests and questionnaires. This is important because some of the tests require automatic and rapid processing of written English.
6. Must have a baseline level of violent video game play averaging less than or equal to 2 hours per week in the year prior to the study, and must have a baseline level of total video game play averaging less than or equal to 5 hours per week in the year prior to the study. These values are based on research by Kronenberger et al. (2005a) showing that nonviolent control adolescent subjects averaged about 2-3 hours of video game play in a week (of which 1-2 hours are spent with violent video games), compared to aggressive adolescent subjects, who averaged about 4-7 hours of video game play per week (of which 3-4 hours are spent with violent video games). Green and Bavalier (2003) based their selection criteria for "action video game players" (VGP) on an average of 1 hour per day for 4 days a week of violent/action video game play and found differences between the VGP group and a non-VGP group on visual processing. It is important to select subjects who are not frequent game players in order for the experimental manipulation (8-16 hours of violent video game play) to be different from their baseline behavioral habits.
7. Must be willing to make lifestyle changes about media habits during the 3-5 week duration of the study.
8. Must have basic level of proficiency with computer to load and play video games.

Exclusion Criteria:

1. Organic brain conditions or seizure disorder (history of febrile seizures with no neurological sequelae is acceptable).
2. Any physical condition or risk that would preclude or invalidate an MRI.
3. Any current mental health diagnosis (other than Adjustment Disorder), based on the Adult Inventory - 4 and follow-up questions from the interviewer, which would be defined as moderate or more severe using the Clinical Global Index - Severity.
4. Treatment of a behavioral or emotional problem (excluding normal adjustment issues, such as adjustment to divorce) by a mental health professional in the past year.
5. Any historical diagnoses of Attention-Deficit/Hyperactivity Disorder, Conduct Disorder, Oppositional-Defiant Disorder, Bipolar Disorder, Schizophrenia (or other disorder involving psychosis), Personality Disorders, or Pervasive Developmental Disorders.
6. Any history of Attention-Deficit/Hyperactivity Disorder, Conduct Disorder, Oppositional-Defiant Disorder, Bipolar Disorder, Schizophrenia (or other disorder involving psychosis), Personality Disorders, or Pervasive Developmental Disorders in first degree relatives (mother, father, siblings, children).
7. Current diagnosis of Substance Abuse or Dependence
8. Use of psychotropic medication for treatment of a mental or behavioral disorder at any time in the study or in the year prior to the study.