Friday, December 12, 2014

Guns And Controllers: Do Violent Video Games Cause Aggressive Behaviour? A Review Of Meta-Analytic Research

Let me be upfront concerning my views about this topic. Until now, when I decided to research the evidence and examine its credibility, I never gave much credence to the idea of violent video games causing aggressive behaviour. To me, it just seemed counter-intuitive: now more than ever, children of all demographics and backgrounds are playing video games, and many of the most favoured are clearly violent in nature. Meanwhile, the violent crime rate is decreasing to levels we haven't seen in decades. How could both of these facts be true at the same time if violent video games have significant impacts on behaviour?

The answer is simple: plenty of factors play into crime. While the overall trend may be a decrease in violent crime, there still may be underlying factors which are keeping the rate of its decline lower than may be attainable. Does that mean I think that video games are a terribly important factor for consideration in this sense? Not really. I think that video games have the potential to affect behaviour, but that the real-world implications of this fact are minimal, manifesting in maybe only a handful of cases each year. I do think it has important societal implications in terms of our attitudes towards others, but one could consider these to be superficial concerns.

How likely is this? Would we be willing to accept it?
The implications of the research are not my concern. At present, the evidence for such claims as those above is unclear, and the evidence for behavioural effects from playing violent video games is up for scrutiny in itself. Here, I would like to present the best evidence we presently have available, and review how the academic community sees this issue. Again, I will not be going over what policies should be implemented, if any, in response to the literature; I will only be examining the question itself: do violent video games cause aggressive behaviour?

The short answer is, probably. The long answer is that with the evidence we have, we can confidently state that violent video games have at least a minimal effect, but probably a fairly substantial effect on various behavioural and cognitive traits. Most researchers in this field do not deny the small correlations and causal evidence, but how significant these are depends on who you go to, as stated. The primary debate can be seen among meta-analytic reviews of the data from some prominent researchers of this topic.

The first is Craig Anderson, who has been one of the most significant contributors to the scientific literature in this area. Anderson has conducted two meta-analyses to date of the literature: one in 2001, the other in 2010. The first one, entitled "Effects of Violent Video Games on Aggressive Behavior, Aggressive Cognition, Aggressive Affect, Physiological Arousal, And Prosocial Behavior: A Meta-Analytic Review of the Scientific Literature," was published in the Psychological Science. Here, Anderson and Bushman -- another lead researcher in this field -- reviewed 35 research reports with a total of 4,262 participants, 46% of whom were under the age of 18. In 33 independent tests of 3,033 individuals, they found that video game violence was associated with heightened aggression. They note that the association is as strong as the effect of condom use on risk of HIV infection. They found that this association remained significant across gender, age, and experimental versus non-experimental design, thus showing that violent video games do result in real-world heightened aggression. In addition to this, in 8 independent tests of 676 participants, playing violent video games was negatively correlated with prosocial behaviour in both experimental and nonexperimental designs. In 20 studies of 1,495 participants, there was a causal link between violent video games and aggressive cognition. In 17 tests of 1,151 participants, playing violent video games resulted in aggressive affect. Finally, in 7 tests of 395 participants, violent video games were associated with physiological arousal.

Their second meta-analysis was much more robust, as much research had been conducted since their first analysis with improved methodologies as well. In "Violent Video Games Effects on Aggression, Empathy, and Prosocial Behavior in Eastern and Western Countries: A Meta-Analytic Review," published in Psychological Bulletin, Anderson et al. reviewed 130 research reports of over 130,000 participants. In 70 independent effects of 18,000 participants, violent video games were causally linked to both short-term and long-term aggressive behaviour. In 50 independent effects of over 12,000 participants, violent video games were causally linked to aggressive cognition. In 62 studies of over 17,000 participants, playing violent video games had a causal effect on aggressive affect. In 23 studies of 9,645 participants, violent video games had a negative effect on prosocial behaviour. Again, violent video games also had a causal effect on physiological arousal. Finally, presented as a new outcome variable in 32 studies of 8,528 participants, playing violent video games was causally linked to a decline in empathy and an increase in desensitization to violence. All of these effects existed regardless of country, culture, age, sex, or study design.

Craig Anderson, a.k.a. "The Target"
The latter of these two studies is considered to be paramount in this debate, as it seems to have the most superior study design. Some have criticized the methodology, although the arguments are not very strong. The first argument is that the study authors had to decide which methodologies were superior to others, and so the effect sizes increased to which studies they favoured, suggesting effect bias. This isn't an argument anyone familiar with meta-analytic research would make. If there is any question of whether or not the effect sizes granted to different studies was flawed, one can always read the methodology report. In this case, Anderson et al. excluded studies which included pilot testing of nonviolent video games and as well as studies which tested, for example, the physiological arousal of participants who played nonviolent video games as well as violent video games. If you wish to read their methodology, it's available, but there is nothing to suggest that it's unsound.

The other argument presented in the article was that Anderson et al. included unpublished studies as well as published studies. Intuitively, this may seem like a valid point: if a study wasn't good enough to get published, then why should it be given considerable weight in comparison to published studies? The fact is, however, that this is also not a reasonable argument in terms of meta-analytic analysis. While differences exist between meta-analytic researchers and editors of journals which publish these meta-analyses, the overall attitude is that the use of unpublished studies in meta-analytic reviews is preferable to account for publication biases.

In fact, this was a major flaw in one of the competing meta-analytic reviews of the literature in this field. The lead study author for these studies was Christopher Ferguson, who can be viewed as the antithesis of Anderson. One of his own criticisms of Anderson's meta-analyses was that half of the studies he cites are conducted by himself. Again, this seems suspect at a visceral level, but is not faulty methodology as far as I know. Ferguson actually published two meta-analytic reviews of the scientific literature, but I can only seem to find access to the more recent one from 2009. Both had the flaw of not including unpublished studies, but we will review Ferguson's research as it's still important.

Ferguson's meta-analysis was entitled "The Public Health Risks of Media Violence: A Meta-Analytic Review," and was published in The Journal of Pediatrics. As stated, unlike Anderson's meta-analyses, Ferguson excluded unpublished papers, but claimed that this is standard meta-analytic procedure, and that they did this because they included an analysis on publication bias. They also excluded papers from before 1998, as they alleged the outdated methodologies may "pollute" the results. Ferguson and Kilburn examined 27 studies of an unspecified number of participants, though only 15 of the studies dealt with video games. The results show that the studies display a minimal correlation between playing video games and aggressive behaviour, and that the effect size (as well as the strength of the correlation) highly depend on the methodology. They discuss multiple criticisms of Anderson & Bushman's meta-analysis in 2001, but Anderson et al. addressed most of these criticisms in their 2010 study. In addition, Rowell Huesmann published a response to critiques of Anderson's 2010 meta-analysis.

And in this corner... Christopher Ferguson
As we can see, Ferguson's study is limited by sample size compared to the two meta-analyses led by Anderson. It should not be discounted, however, simply for its limitations -- it should only be noted that the weight of Ferguson's study may not be comparable to Anderson's studies. I'll admit, there is quite a heated battle between these two individuals, and so it would be beneficial to briefly defer to other reviews of the literature, namely two that have gotten the most attention.

The first one, entitled "Violent Video Games and Aggression: Why Can't We Find Effects?" was published by John Sherry in 2007. His goal was to challenge multiple theories of media impacts on violence and see if the evidence was consistent with them. He concluded that there was a minimal effect on behaviour by violent video games, and suggested that perhaps previous findings were amplified by methodologies. One example he gave was for exposure time: studies which had longer exposure times had smaller effect sizes, suggesting that the effects decrease over time. This isn't terribly inconsistent with prior findings, but Anderson et al. (2010) divided their results by study design and found that the effect persists even in longitudinal studies.

The other meta-analysis has a lot more to discuss. Published by Greitemeyer and Mügge, the study was entitled "Video Games Do Affect Social Outcomes: A Meta-Analytic Review of the Effects of Violent and Prosocial Video Game Play" and was published in the Personality and Social Psychology Bulletin this year, making it the most recent meta-analysis to date. The authors reviewed 98 independent studies of 36,965 participants to test both positive and negative social outcomes. Separate meta-analyses were conducted for violent and prosocial video game exposure. They note that the effects for both outcomes were reliable across experimental, correlational and longitudinal studies. Consistent with Sherry (2007), they found that studies with longitudinal designs had the lowest effect sizes, while experimental designs had the highest. In 43 independent studies of 21,215 participants, violent video games significantly effected violent behaviour. At the same time, in 6 independent studies of 693 participants, prosocial video games inspired prosocial behaviour, meaning that video games can play an effect on social outcomes regardless of what that outcome is. It could be argued (and I would agree) that a balance should be struck: violent video games should perhaps look into ways to incorporate prosocial behaviour while maintaining their violent nature for players who are interested in that type of game. Some studies have actually suggested this, but the overall effect is clear based on the data that violent video games cause a significant effect on social outcomes.

There are a lot of recent studies examining the relationship further, many of them conducted by Ferguson or Anderson, but I think I've covered enough ground here. Some individuals are not convinced by the literature, especially those (such as myself) who don't want to admit that some of their favourite video games have negative effects on social outcomes and may play a role, in some cases, in violent actions. In these cases where emotion clouds reason (again, such as in my own case), it's always informative to look at what the academic consensus is by looking to relevant scientific organizations and their public statements on the issue.

Without fail, the American Psychological Association (APA) released such a policy statement in 2005. The statement reads that violent media across all mediums has a significant effect on aggressive behaviour, but there exists some nuance. For example, in the 16% of media depictions where violent behaviour is punished either physically or financially, it can actually inhibit aggressive or violent behaviour. Overall, however, the literature suggests that media does play a role in individual behaviour, psychology and social outcome.

This statement did not go without criticism. In response, Ferguson led an international group of 228 media scholars, psychologists and criminologists to suggest that the APA revise their statement to address recent literature and possible methodological flaws in past studies. The statement is now up for review, a task force has been appointed to review the literature, and a revised statement is expected to be published some time this year; although, since it's December, I don't know how feasible that is. I will post the results at the bottom of this article if and when it comes up.

So, if we want to individually look at the scientific literature, it seems that there is substantial evidence that violent video games do cause aggressive behaviour and other psychological effects, but that there may be some flaws in methodology, some overlooked studies, biases, etc. which may exaggerate how great the effect is. If we want to go by the consensus, it seems that there may not be one; however, as of 2005, the APA stance was in support of this interpretation of the literature. In addition, APA Executive Director of Science Steven J. Breckler expressed support of their prior conclusions, noting: "since then, the literature has evolved and, if anything, adds more support to that position. Nevertheless, this is an area of ongoing research, and other perspectives are emerging." To offer support to the opposing side, the author of that article suggests that there is disagreement among researchers. Of course I would agree with this conclusion; however, how broad that disagreement is, and whether or not it is a representation of the literature is up for interpretation.

As much as I don't want it to be true, if one goes by the evidence or the APA's stance on the issue, it seems the only justifiable conclusion is that violent video games probably do cause aggressive behaviour and violent outcomes. How this effect manifests in different individuals, however, is up for debate and individual examination. I personally think that it is most likely to manifest in already desensitized individuals or those who are prone to such behaviours or outcomes, but the data seems to suggest that it goes beyond that. The concern now should be on settling the debate and further researching just how great these effects are, and what the implications are for real-world practices. Even if one doesn't like the findings of the research, it's important to not let our biases get in the way of objectivity and truth. Things can't always be what we want them to be.

I wish that other researchers would look more deeply into dissent and find the reasons for it, and give more credence to the opposing views. At the end, the author of that article states that violent video games without a doubt cause aggressive behaviour, and "don't believe anyone who tells you otherwise." This attitude seems unwarranted; while the research does lend more credence to her position, researchers shouldn't poison the well and act like the debate is absolutely settled and that anyone who doesn't think so is dishonest. That stance is dishonest, since the data is still under review. In the end, the only solution for the debate is time.

Thank you all very much for reading.

[EDIT (12/30/15): I have written an article in regards to the APA's new resolution and report on this topic. You can read it here.]

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ResearchBlogging.orgAnderson, CA & Bushman, BJ (2001). "Effects of Violent Video Games on Aggressive Behavior, Aggressive Cognition, Aggressive Affect, Physiological Arousal, And Prosocial Behavior: A Meta-Analytic Review of the Scientific Literature." Psychological Science DOI: 10.1037/e315012004-001

Anderson CA, Shibuya A, Ihori N, Swing EL, Bushman BJ, Sakamoto A, Rothstein HR, & Saleem M (2010). "Violent video game effects on aggression, empathy, and prosocial behavior in eastern and western countries: a meta-analytic review." Psychological bulletin, 136 (2), 151-73 PMID: 20192553

Ferguson, C., & Kilburn, J. (2009). "The Public Health Risks of Media Violence: A Meta-Analytic Review." The Journal of Pediatrics, 154 (5), 759-763 DOI: 10.1016/j.jpeds.2008.11.033

Greitemeyer, T., & Mugge, D. (2014). "Video Games Do Affect Social Outcomes: A Meta-Analytic Review of the Effects of Violent and Prosocial Video Game Play." Personality and Social Psychology Bulletin, 40 (5), 578-589 DOI: 10.1177/0146167213520459

Huesmann, L. (2010). "Nailing the coffin shut on doubts that violent video games stimulate aggression: Comment on Anderson et al. (2010)." Psychological Bulletin, 136 (2), 179-181 DOI: 10.1037/a0018567

Sherry (2007) was omitted from the sources since I couldn't find the DOI. This source is problematic for several reasons, including its lack of accessibility. I may consider omitting it from the article in the future depending on whether or not it becomes problematic.

*Additional studies have been mentioned in the comments section. I would suggest giving them a look to get a full review of the literature, as the above article is not comprehensive.*


  1. Very informative review of the literature, although you forgot Sherry 2001 which supported the correlation, K = 25, N = 2,722. Ferguson 2007 can be found here:

    And here is the first study:

    I really would have liked to see you discuss the weightings of effect sizes and the correlational strengths the different reviews found, since that is of important consideration as well, and at present we have such estimates. I agree with your sentiments concerning prior desensitization and susceptibility to effect outcomes from playing violent video games. I think this trend reflects a recent change in the socialization and development of children (and then adults), as even from a young age we are desensitized to scenarios and events which decades ago would be seen as so detestable to even look at. One only needs to look at how much detail is put into the news concerning homicides of all types to understand the amount of gore we are exposed to nowadays.

    It's a shame so many people despise Anderson. I don't think that the flaws in his methodology are really that detrimental overall considering the size and scope of his meta-analytic reviews; however his funding should be considered...

    1. It honestly would have taken far too long to discuss all of the details of the effect outcomes found in the studies, but I do recommend to everyone who's interested in this topic to read the meta-analytic reviews and find out for themselves. Thank you for the resources, Brutal, and I'll look into what you noted about Anderson.

  2. I was under the same impression you were before you made this post. It kinda sucks, but at least now we know the facts.

    I've got a question. What is your opinion on the war between Ferguson and Anderson? Do you think one of them has a chip on their shoulder, or do you think they've got a love-hate thing going? Honestly both of them seem gay for their own reasons, but I'm more inclined to trust the punchable face of Ferguson rather than pedo Anderson.

    1. (rolleyes) Shut up, Nick. I don't know if either of them have a bias, but I think it's interesting that there does seem to be a Ferguson vs Anderson paradigm to this debate. I don't think there's any reason to side with one individual or another, or make claims about one individual's biases over another. It should be based on the credibility of the literature, not the personalities of the researchers.

  3. Thanks for doing this and will share. I recently attended a training on video game / addiction. The conclusion they came to is that we need to be more concerned about length of exposure. Similar to paying attention to our children's food diet, we need to monitor their "media diet". How much media are the taking in and how. Have honest discussions about this issue and limit media accordingly. this can be tricky but worth it in the end.

    1. Responded on your website. Again, thank you for sharing!

  4. It has always seemed to me very one sided to accuse games or movies for violence. However I think with children who are already problematic then we can question if violent games are good or bad. To what point do they help people release anger and after what point do they actually feed it?

    1. Comment permitted because it only tangentially seems like spam.

      One sided how? Of course violent media will have a stronger effect on children who are already disturbed and are disconnected from reality, but one can't simply ignore the data and claim this is the only situation where we should examine whether or not violent media causes violence. It also isn't the only cause of violence, mind you. That would run afoul with decades of research in criminology.

      As for your point on the upper/lower fence for catharsis versus instigation, this was somewhat reviewed in the article. I would more closely read Greitemeyer and Mügge (2014).


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