PSYCHOLOGICAL SCIENCE

Research Report Deciding to Defect The Effects of Video-Game Violence on Cooperative Behavior Brad E. Sheese and William G. Graziano

Purdue University

ABSTRACT—This experiment examined the effect of video- This study examined how video-game violence affects delib- game violence on cooperative decision making. Partici- erate decisions to behave cooperatively or competitively and pants (N 5 48) were randomly assigned to play either a expectations about how other individuals will behave. On the violent or a nonviolent version of the video game Doomt in basis of the GAM, we made two hypotheses. The first hypothesis dyads. Following the video-game task, participants were was that playing a violent video game would cause participants to separated and given an opportunity to choose to cooperate anticipate less cooperative and more competitive behavior from with their partner for mutual gain, withdraw from the interaction partners. The second hypothesis was that playing a interaction, or exploit their partner for their own benefit. violent video game would cause participants to choose to com- Participants in the violent condition were significantly pete, rather than cooperate, in subsequent interactions. more likely to choose to exploit their partners than par- Weused a modified Prisoner’s Dilemma (PD) game to examine ticipants in the nonviolent condition. These findings sug- competitive and cooperative decision making. The PD has been gest that playing violent video games may undermine used extensively in previous research to examine conditions prosocial motivation and promote exploitive behavior in that promote mutual cooperation (Axelrod & Hamilton, 1981). social interactions. For the current study, we used a modified version of the PD (PD- ALT; Insko, Schopler, Hoyle, Dardis, & Graetz, 1990) that al- lowed participants to choose among cooperating, defecting, and Recent research has found a positive association between withdrawing. In a traditional PD decision matrix, a decision to playing violent video games and aggressive feelings and be- defect may reflect either a decision to exploit a partner who is haviors (e.g., Anderson et al., in press; Bushman & Anderson, trusted or a decision to defend oneself from an exploitive in- 2002; Sherry, 2001). Recent research has also provided initial teraction partner. In PD-ALT, a ‘‘withdraw’’ choice that presents evidence of a negative association between playing violent an intermediate level of reward is available, making it possible video games and prosocial behavior (Anderson & Bushman, to distinguish between participants who trust their partners but 2001; Ballard & Lineberger, 1999; Wiegman & VanSchie, want to exploit them and participants who do not trust their 1998). According to the General Aggression Model (GAM; partners. The matrix is designed so that if participants do not Anderson & Bushman, 2002), one way that exposure to violent trust their partners, they should choose the option labeled ‘‘Y’’ media may be linked to both pro- and antisocial behavior is (the withdrawal option). If participants do trust their partners through the activation of aggression-related schemas that are and want to cooperate, they should choose the option labeled stored in memory. The activation of these schemas may alter the ‘‘X’’ (the cooperation option). If participants trust their partners way subsequent information is processed, such that neutral or but want to exploit them, they should choose the option labeled ambiguous cues may be interpreted as threatening or aggres- ‘‘Z’’ (the defection option). sive. Consequently, the activation of aggression-related sche- The PD-ALT decision matrix allowed us to examine how mas may alter appraisal and decision-making processes, playing violent video games affected trust and decisions to ultimately leading to more antisocial, and fewer prosocial, defect separately. Additionally, prior to making a decision for behaviors. themselves, participants were asked to anticipate their partner’s decision. Examining the participants’ predictions and decisions Address correspondence to Brad E. Sheese, Department of Psycho- separately provided a direct method for testing the hypothesis logical Sciences, Purdue University, 703 Third St., West Lafayette, IN 47907-2004; e-mail: [email protected]. DOOM is a regis- that violence should affect the participants’ perceptions of other tered trademark of Id Software, Inc. individuals’ intentions.

354 Copyright r 2005 American Psychological Society Volume 16—Number 5 Brad E. Sheese and William G. Graziano

On the basis of the PD-ALT framework and our predictions Teams were initially trained on how to play the video game derived from the GAM, we anticipated the following pattern of and were familiarized with the rules and objectives. They were outcomes. First, we hypothesized that, relative to participants then given 25 min to complete as many mazes as possible. who played a nonviolent video game, those who played a violent After 25 min had elapsed, the participants were separated. video game would be significantly more likely to anticipate that They were then presented with the PD-ALT decision matrix, their partner would either withdraw or defect. Second, we hy- which showed three choices labeled ‘‘X,’’ ‘‘Y,’’ and ‘‘Z.’’ They pothesized that participants would be significantly more likely were told that the total number of points they had earned would to choose to defect if they played a violent video game than if be multiplied by a fixed amount, determined by their decision they played a nonviolent game. and their partner’s decision. If both partners decided to pick X To test these hypotheses we developed a specially modified (cooperate), both partners’ scores would be multiplied by a version of the video game Doomt. In the nonviolent version of moderate amount (1.5). If both partners picked Z (defect), then the game, participants were asked to find the end of a three- both partners would lose half their points (i.e., their scores dimensional maze. In the violent version of the game, partici- would be multiplied by 0.5). However, if one partner chose to pants were asked to find the end of the same three-dimensional cooperate and the other chose to defect, the defecting partner’s maze, but weapons and simple computer-controlled opponents score would be multiplied by a large amount (2), whereas the were also introduced. The opponents, various kinds of fictional cooperating partner would lose half of his or her points. Finally, monsters, were easy to kill with the available weapons and did if either partner picked Y (withdraw), both partners’ scores not present a significant challenge to the participants. They did, would remain the same (i.e., their scores would be multiplied however, present players with an opportunity to shoot and kill by 1). opponents while in the process of finding their way through the After successfully completing a brief quiz, to show they un- maze. derstood the instructions and the decision matrix, participants were asked to anticipate what choice their partner would make. Finally, they were asked to make the decision for themselves. METHOD RESULTS Participants Undergraduate students (N 5 48; 6 women) participated in The participants’ predictions of their partners’ choices were pairs. Participants were primarily (80%) non-Hispanic whites. used to calculate two outcome variables. Predicted trust, indi- cating whether participants anticipated that their partners would trust them and not withdraw, was scored as follows. Participants who anticipated that their partners would pick Procedure either Choice X (cooperate) or Choice Z (defect) received a Two participants, who were unfamiliar with one another, were score of 1 for predicted trust; participants who anticipated that brought into a lab setting and randomly assigned to be either their partners would pick Choice Y (withdraw) received a score ‘‘Player A’’ or ‘‘Player B.’’ They were told that they would be of 0. Of the 48 participants, 42 anticipated that their partners competing with all of the other study participants who had the would trust them (21 in the violent condition, 21 in the nonvi- same designation, but that they were not competing with each olent condition). Predicted defection, indicating whether the other. It was explained that when the study was completed, both participants anticipated that their partners would choose to the best-performing Player A and the best-performing Player B defect, was scored as follows. Participants who anticipated that would be awarded $100. their partners would pick Choice Z (defect) received a score of Teams were then asked to play a multiplayer video game, 1; participants who anticipated that their partners would pick Doomt, in which they would complete a series of three-di- Choice X (cooperate) or Choice Y (withdraw) received a score of mensional mazes. They were told that they would earn points for 0. Of the 48 participants, 3 anticipated that their partners would every maze they completed within 25 min. Both players had to choose to defect (2 in the violent condition, 1 in the nonviolent reach the end of a given maze before the pair could advance to condition). the next maze. The participants’ own decisions using the PD-ALT matrix Teams were randomly assigned to play either a violent or a were also used to calculate two outcome variables. The trust nonviolent version of Doomt. In the two conditions, the mazes score, reflecting whether the participant trusted his or her and the goal of the game were identical. However, in the violent partner and did not withdraw, was 1 for participants who picked condition, both players were provided with weapons, and the either Choice X (cooperate) or Choice Z (defect) and 0 for mazes included opponents that would attack the two players. In participants who picked Choice Y (withdraw). Of the 48 par- the nonviolent condition, players had no weapons, and there ticipants, 43 chose to trust their partner and not withdraw (23 in were no opponents within the mazes. the violent condition, 20 in the nonviolent condition). The

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defection score, reflecting whether or not the participant chose Playing a violent video game appears to have contributed to defect, was 1 for participants who picked Choice Z (defect) directly to participants’ willingness to exploit their interaction and 0 for participants who picked Choice X (cooperate) or partners. However, contrary to predictions, there was no evi- Choice Y (withdraw). Of the 48 participants, 8 chose to defect (7 dence that playing a violent video game altered participants’ in the violent condition, 1 in the nonviolent condition). perceptions of what their partners would do. Participants in the Nonindependence was assumed, because there was an in- violent condition were not any more likely than those in the sufficient sample size to test the independence of the partici- nonviolent condition to think that their partners would exploit pants on each of the dependent variables with a power equal to them or distrust them. Instead, participants in both conditions or greater than .80 (Kenny, Kashy, & Bolger, 1998). Multilevel generally expected that their partners would trust them and modeling (Raudenbush & Bryk, 2002), conducted with HLM cooperate with them. However, participants in the violent (Version 5.05; Raudenbush, Bryk, Cheong, & Congdon, 2000), condition were more likely than those in the nonviolent con- was used to assess the effect of the manipulation of video-game dition to exploit that trust and choose to defect. This pattern of violence on each of the four dependent variables. Nonlinear results suggests that playing a violent video game may have an models were specified because the dependent variables were effect on cooperative behavior independent of alterations in the binary. Models were specified such that individual participants perceptions of other people’s motives. were nested within pairs. The condition (violent or nonviolent) Anderson and Morrow (1995) suggested that the activation of was dummy-coded and modeled as a fixed effect. competitive knowledge structures can lead directly to aggres- There was no evidence to indicate that participants assigned sion. Their findings were consistent with this hypothesis: In to the violent condition (M 5 .86, SD 5 .34) were less likely comparison with priming cooperation, priming competition led than participants assigned to the nonviolent condition (M 5 .86, to more aggressive behavior in a subsequent video game, but did SD 5 .34) to anticipate that their partner would trust them, B 5 not affect friendliness, liking, or hostility toward an interaction 0.00, t(46) 5 0.00, p 5 1.00, d 5 0.00. There was also no partner. Our results suggest that the opposite may also be true, evidence to indicate that participants assigned to the violent that participating in violent game play may encourage people to condition (M 5 .04, SD 5 .20) were more likely than partici- compete. In the current study, the addition of violent game play pants assigned to the nonviolent condition (M 5 .08, SD 5 .06) into the cooperative maze task may have served to prime to anticipate that their partner would defect, B 5 0.74, t(46) 5 competitive knowledge structures that were applied to the 0.63, p 5 .53, d 5 0.19. Overall, there was no indication that subsequent PD-ALT interaction. playing the violent version of the video game caused partici- If this interpretation is correct, then the current findings are pants to anticipate less cooperation or prosocial behavior from remarkable considering that, in both conditions, participants their partners. played a cooperative video game for 25 min before making their A different pattern emerged in the participants’ own choices. decision. It could be plausibly argued that cooperatively en- There was no evidence to indicate that participants assigned to gaging in violent behavior against a common enemy would ac- the violent condition (M 5 .96, SD 5 .20) were more likely than tually increase feelings of cohesion and camaraderie and participants assigned to the nonviolent condition (M 5 .83, SD promote subsequent cooperation (e.g., Deutsch, 1993; Sherif & 5 .08) to not trust their partner and choose to withdraw, B 5 Sherif, 1953). However, the current results indicate that en- 1.53, t(46) 5 1.73, p 5 .18, d 5 0.51. However, participants gaging in violent game play prompts the opposite pattern of assigned to the violent condition (M 5 .29, SD 5 .46) were behavior. Violence, even when directed at third parties, appears significantly more likely than participants assigned to the to be effective at undermining the emergence of cooperative nonviolent condition (M 5 .04, SD 5 .20) to choose to defect, patterns of interaction. B 5 2.24, t(46) 5 2.23, p 5 .03, d 5 0.66. The results presented here must be considered in light of several limitations. First, the sample size of the current study was insufficient for reliably detecting effects that are small or CONCLUSIONS even moderate in size. Consequently, caution is warranted in interpreting the null effects reported. A second limitation is that The current study is consistent with previous research indi- the findings may have limited generalizability because the study cating that playing violent video games may have negative ef- used a convenience sample of undergraduate students who were fects on social behavior. The current study also extends predominantly White males. Furthermore, given that the study previous research by showing how playing violent video games was conducted using dyads only, it is not clear if the effect may affect subsequent decisions to cooperate or compete with would generalize to single-player situations. Social interaction other individuals in high-stakes situations. More generally, the during the violent game play may have been an important factor current findings suggest that playing violent video games may in subsequent decisions to defect. A third limitation is the molar undermine prosocial and altruistic motivation and promote nature of the manipulation. The addition of weapons and competitive behavior in deliberate decision making. monsters altered the basic maze task in a variety of ways.

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Consequently, additional research will be needed to determine Specific effects of violent content on aggressive thoughts and if it was the full manipulation or just a specific aspect of it that behavior. Advances in Experimental Social Psychology. was responsible for the observed effect. Anderson, C.A., & Morrow, M. (1995). Competitive aggression without interaction: Effects of competitive versus cooperative instructions Despite these limitations, the pattern of results is provocative on aggressive behavior in video games. Personality and Social and worthy of additional study. Unlike in many of the published Psychology Bulletin, 21, 1020–1030. studies in this area, participants in the current study were not Axelrod, R., & Hamilton, W.D. (1981). The evolution of cooperation. asked either to aggress against or to punish other people. In- Science, 211, 1390–1396. stead, they were given an opportunity to exploit their interaction Ballard, M.E., & Lineberger, R. (1999). Video game violence and partners to earn a substantial sum of money for themselves. The confederate gender: Effects on reward and punishment given by college males. Sex Roles, 41, 541–558. current study shows clear evidence that engaging in violent Bushman, B.J., & Anderson, C.A. (2002). Violent video games and game play makes people more likely to deliberately choose to hostile expectations: A test of the general aggression model. exploit their partners in this situation. Future research should Personality and Social Psychology Bulletin, 28, 1679–1686. focus on examining further the psychological mechanisms, such Deutsch, M. (1993). Educating for a peaceful world. American Psy- as aggressive cognitions, hostile affect, and increased physio- chologist, 48, 510–517. logical arousal (e.g., Anderson & Bushman, 2002), that may Insko, C.A., Schopler, J., Hoyle, R., Dardis, G., & Graetz, K. (1990). Individual-group discontinuity as a function of fear and greed. account for this finding. Journal of Personality and Social Psychology, 58, 68–79. Kenny, D.A., Kashy, D.A., & Bolger, N. (1998). Data analysis in social Acknowledgments—The authors thank Joshua Chartier and psychology. In D. Gilbert, S. Fiske, & G. Lindzey (Eds.), The Joey Mignogna for their invaluable assistance in conducting handbook of social psychology (4th ed., pp. 233–265). New York: this research. We also thank Jeremy Biesanz, Thomas Berndt, McGraw-Hill. Raudenbush, S.W., & Bryk, A.S. (2002). Hierarchical linear models: and George Hollich for their thoughtful suggestions. This re- Applications and data analysis methods (2nd ed.). Newbury Park, search was supported by Grant R01-MH50069 from the Na- CA: Sage. tional Institute of Mental Health to William Graziano. Raudenbush, S.W., Bryk, A.S., Cheong, Y.F., & Congdon, R. (2000). HLM 5: Hierarchical linear and nonlinear modeling. Lincolnwood, REFERENCES IL: Scientific Software International. Sherif, M., & Sherif, C.W. (1953). Groups in harmony and tension. New Anderson, C.A., & Bushman, B.J. (2001). Effects of violent video York: Harper. games on aggressive behavior, aggressive cognition, aggressive Sherry, J.L. (2001). The effects of violent video games on aggression: A affect, physiological arousal, and prosocial behavior: A meta- meta-analysis. Human Communication Research, 27, 409–431. analytic review of the scientific literature. Psychological Science, Wiegman, O., & VanSchie, E.G.M. (1998). Video game playing and its 12, 353–359. relations with aggressive and prosocial behavior. British Journal Anderson, C.A., & Bushman, B.J. (2002). Human aggression. Annual of Social Psychology, 37, 367–378. Review of Psychology, 53, 27–51. Anderson, C.A., Carnagey, N.L., Flanagan, M., Benjamin, A.J., Eu- banks, J., & Valentine, J.C. (in press). Violent video games: (RECEIVED 6/14/04; REVISION ACCEPTED 9/23/04)

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