<human>:  What scientific studies have been conducted on the long-term psychological effects of playing violent video games?
<bot>: There have been numerous scientific studies conducted on the long-term psychological effects of playing violent video games. In particular, research has focused on the impact of violent video games on aggressive behavior, attitude changes, desensitization to violence, empathy, and the development of pro-social behaviors. For example, a 2019 meta-analysis of 41 studies found that playing violent video games was associated with increased aggressive behavior, aggressive cognitions and aggressive affect, as well as decreased empathy and pro-social behavior. Other research has also suggested an association between playing violent video games and increased likelihood of anti-social behavior, lower self-control and increased aggressive behavior in the long-term.