Final answer:
A weak manipulation might account for Dr. Morimoto not observing a relationship between playing time and aggression, as the 2-minute difference is likely insufficient to measure aggression changes. The relationship between violent video games and aggression is complex, with some studies suggesting a causal link, while others find insufficient evidence of a direct causal connection.
Step-by-step explanation:
Dr Morimoto is curious as to whether exposing people to violent video games causes them to be more aggressive. He finds that there is no relationship between playing the game longer and being more aggressive. Weak manipulation might be to blame for this null effect, as the difference in time spent playing the video game (5 minutes vs 7 minutes) may not be significant enough to observe a measurable change in aggression.
Research on the effects of violent video games on aggression is mixed. Some studies, like those by Anderson and Bushman (2001), suggest a causal link between violent video game exposure and increased aggression, while other researchers like Christopher Ferguson indicate that there may be a correlation, but not necessarily a direct causal link, as factors like mental health and family life have not been fully considered.
Moreover, while the American Psychological Association and Anderson's research indicated a potential increase in aggressive tendencies, other studies, including a meta-analysis covering four decades, could not definitively conclude that violent video games lead to an increase in criminal violence. These conflicting findings indicate that the subject is complex and other variables could also contribute to aggressive behavior.