This chapter examines the cognitive and brain effects of playing a specific game genre—namely action video games. Video games are now played extensively around the world. Indeed, defying the common stereotype of video games being “just for kids” or “just for boys”, video games are played by an exceptionally broad swath of the population. When discussing the impact that video games have on the brain and cognition, it is important to recognize that the label “video games” encompasses an incredibly wide variety of experiences. To investigate the effects of action video game play on behavior, one—often initial—approach has consisted in utilizing a cross-sectional design. Demonstrating a causal relation requires running an intervention or training study. Intervention studies involve recruiting participants who have at most limited video game experience. The large difference in amount of action game experience is likely to at least partially explain the lower effect sizes in intervention as compared to cross-sectional studies.