title: Longitudinal effects of violent video games on aggression in Japan and the United States.
abstract: BACKGROUND
  Youth worldwide play violent video games many hours per week. Previous research suggests that such exposure can increase physical aggression.
  
  
  OBJECTIVE
  We tested whether high exposure to violent video games increases physical aggression over time in both high- (United States) and low- (Japan) violence cultures. We hypothesized that the amount of exposure to violent video games early in a school year would predict changes in physical aggressiveness assessed later in the school year, even after statistically controlling for gender and previous physical aggressiveness.
  
  
  METHODS
  In 3 independent samples, participants' video game habits and physically aggressive behavior tendencies were assessed at 2 points in time, separated by 3 to 6 months.
  
  
  METHODS
  One sample consisted of 181 Japanese junior high students ranging in age from 12 to 15 years. A second Japanese sample consisted of 1050 students ranging in age from 13 to 18 years. The third sample consisted of 364 United States 3rd-, 4th-, and 5th-graders ranging in age from 9 to 12 years. RESULTS. Habitual violent video game play early in the school year predicted later aggression, even after controlling for gender and previous aggressiveness in each sample. Those who played a lot of violent video games became relatively more physically aggressive. Multisample structure equation modeling revealed that this longitudinal effect was of a similar magnitude in the United States and Japan for similar-aged youth and was smaller (but still significant) in the sample that included older youth.
  
  
  CONCLUSIONS
  These longitudinal results confirm earlier experimental and cross-sectional studies that had suggested that playing violent video games is a significant risk factor for later physically aggressive behavior and that this violent video game effect on youth generalizes across very different cultures. As a whole, the research strongly suggests reducing the exposure of youth to this risk factor.
authors.affiliation: Department of Psychology,Center for the Study of Violence, Iowa State University, Ames, Iowa 50011, USA. caa@iastate.edu
authors.forename: Craig A
authors.initials: CA
authors.lastname: Anderson
authors.forename: Akira
authors.initials: A
authors.lastname: Sakamoto
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Gentile
authors.forename: Nobuko
authors.initials: N
authors.lastname: Ihori
authors.forename: Akiko
authors.initials: A
authors.lastname: Shibuya
authors.forename: Shintaro
authors.initials: S
authors.lastname: Yukawa
authors.forename: Mayumi
authors.initials: M
authors.lastname: Naito
authors.forename: Kumiko
authors.initials: K
authors.lastname: Kobayashi
mesh_terms: D000293:Adolescent; D000374:Aggression; D002648:Child; D003469:Culture; D005260:Female; D006801:Humans; D007564:Japan; D008297:Male; D014481:United States; D018910:Video Games / Q000009:adverse effects* / Q000523:psychology; D014754:Violence