One of the topics that's conspicuously absent from my writings on the psychology of video games is that of the relationship between violence and video games. The short version of the reason why is that I think the issue is too polarizing and too much tends to get read into findings on either side.Something I did recently find worth discussing, however, is a kind of inversion of that topic: does playing cooperative games make you less likely to be aggressive and more likely to cooperate with people outside of the game? A big tip of the hat to Wai Yen Tang over at the blog VG Researcher, who recently wrote about three recent studies that explored this topic.The earliest of these studies was by Mike Schmierbach (2010), who was interested in how game mode (single player, coop, or competitive) affected aggression. He shoved subjects into rooms to play games ofon the Xbox either campaign solo, campaign coop, or Slayer mode. After playing for a while, the researcher gave subjects surveys that measured various cognitions and emotional states. One part of the survey involved a word completion task where perplexed respondents were given two letters --KI, DE, BL, etc.-- and then asked to use them to complete any word they liked. If you wrote KILL, DEATH, and BLUDGEON then you got more points than someone who said KISS, DEAN, and BLOKBUSTER. Also, you're a better speller.Schmierbach found that, as expected, people who played a coop mode were far more likely to come up with non-violent words, which he took as evidence of less "aggressive cognition." Other self reported measures of frustration and arousal (in the general physiological sense) showed similar results.This is interesting, but like most people I'm generally more interested in actual behavior than simple internal thoughts or emotional states. Fear not, because this year has seen the publication of two other studies that follow the same basic reasoning as Schmierback's research, but which actually look at whether people engage in more cooperative behavior after setting the controller down.Both Greitmeyer, Traut-Mattausch, and Osswald (2012) and Ewoldson et al. (2012) had subjects start off by playing games like, andin either a competitive or cooperative modes. One unlucky group of people in a control condition got to play Tetris and frown at each other. Both sets of studies then had players set down the controllers and take part in social dilemma type games (of the non video game variety) where they had the chance to either cooperate with other players or screw them over.Ewoldsen et al. found that players who had played the coop video game were more likely to engage in "tit-for-tat" strategies where they would open by cooperating and then either reward or punish the other player depending on if they played competitively or cooperatively in turn. Such a gambit is a very common tactic for players looking to cooperate and maximize outcomes for everyone involved.Greitemeyer and his colleagues took things a bit further and measured perceptions of things like group cohesion (or dyad cohesion if you want to be pedantic about it; I don't) and trust between players. Again, after teaming up to do violence to some common foe, people felt more cohesion and were more trusting in the subsequent task. And it's important to note that these were all violent games --they were just ones that could be played in a helping, cooperative context.There are some interesting takeaways and ideas from this in terms of crafting your own gaming experiences and for developers looking to capitalize on these findings. One is that timing matters. These effects are typically short lived, so if you want to hit players up for things that require cohesion, trust, and cooperation do it right after they've collaborated or interacted with each other in a cooperative way.It's the ideal time to ask them to do things like send/accept friends requests, bestow gifts, heal each other, join groups, trade items, and so forth. Just finished a quest in a pickup group or successfully defended a capture point with the help of a new buddy? That may be the perfect time to pop up a prompt to "Rate this player" or to trade crafting materials. Better than after one of you won a dogfight or shootout against each other.Similarly, if you're a player try not to let the fact that you're competing against someone keep you from cooperating with them next round or accepting their friend request. They may be a pretty cool dude or gal once you're wearing the same colored uniforms.REFERENCESEwoldsen, D. R., Eno, C. A., Okdie, B. M., Velez, J. A., Guadagno, R. E., & DeCoster, J. (2012). Effect of playing violent video games cooperatively or competitively on subsequent cooperative behavior.(5), 277-280.Greitemeyera, T., Traut-Mattauschb, E., Osswaldc, S, (2012). How to ameliorate negative effects of violent video games on cooperation: Play it cooperatively in a team.(4), 1465-1470.Schmierbach, M. (2010). "killing spree": Exploring the connection between competitive game play and aggressive cognition.(2), 256-274.