The effect of out-group competition on individual behavior and out-group perception in the Intergroup Prisoner’s Dilemma (IPD) game

The effect of out-group competition on individual behavior and out-group perception in the Intergroup Prisoner’s Dilemma (IPD) game1 Harel Goren The Hebrew University of Jerusalem Center for Rationality and Interactive Decision Theory and the Department of Psychology Biographical note: The author received his Ph.D in social psychology from The Hebrew University of Jerusalem and has recently finished a one year post-doctoral visit to The Department of Management and Policy at The University of Arizona Abstract Hebrew University of Jerusalem students participated in two experiments of repeated play of the Intergroup Prisoners’ Dilemma (IPD) game, which involves conflict of interests between two groups and, simultaneously, within each group The experiments manipulated the level of competition exhibited by the out-group members (i.e., their level of contribution to their group’s effort in the conflict) Consistent with the hypothesis that participants use strategies of reciprocal cooperation between groups, higher levels of out-group competition caused participants to increase their contribution and lower levels caused them to decrease it In addition, participants had accurate recall of the contribution levels of out-group members, and they attributed motivations to out-group members in a manner that reflected their level of contribution The nature of reciprocation with the out-group is discussed in light of both behavioral and cognitive data Key words: Intergroup conflict, Team games, Prisoner’s dilemma, reciprocal strategies, Intergroup perception Introduction What motives govern individual behavior in intergroup conflicts? The answer to this question depends to a large extent on how the conflict is conceptualized Social scientists have often modeled intergroup conflict as a two-person game (Allison, 1971; Axelrod, 1984; Brams, 1975; Snidal, 1986), necessarily assuming that the interest of the individual is identical to that of his group Thus, if it is rational for the group to compete it must also be rational for the individual group member to so Other researchers recognized that what is best for the group is not necessarily best for the individual group member Most notably, Campbell (1972) observed that contribution to the collective group effort is not rational from the perspective of the individual since “Group-level territoriality has always required that the soldier abandon for extensive periods of time the protecting of his own wife, children and home” (p 24) The conflict between individual interest and group interest referred to by Campbell (1972) is a problem of public goods provision (Rapoport and Bornstein, 1987; Bornstein, 1992) It stems from two facts First, the payoffs associated with the outcomes of inter-group conflicts (e.g., territory, political influence, higher wages) are equally available to all the members of a group, regardless of their contribution to the group’s effort Second, although the size of these public goods increase the more group members contribute, the individual’s contribution to the group’s effort is typically too costly (in terms of money, time, effort or risk taking) to be justified on a rational basis Therefore, self-interested rational group members are expected to free ride on the contribution of others Of course, if everyone else free ride as well, the group would lose the competition and the public goods To capture the intra-group and inter-group levels of conflict, Bornstein (1992) devised the Intergroup Prisoner’s Dilemma (IPD) Game The game as operationalized in the present study involved a competition between two teams with three players in each team Each player received an endowment of points and had to decide whether or not to contribute his endowment towards the group’s effort After decisions were made, a bonus was paid to each player according to following scheme: if all players in Team A contributed, while no players in Team B contributed, each player in A received a bonus of points and each players in B received points If there were more contributors in Team A than in Team B, each player in A received points and each player in B received one point If there was one more contributor in Team A than in Team B, each player in A received points, whereas each player in B received Finally, in case of an equal number of contributors in both teams, each player in both Teams received a 3-point bonus In addition to the bonus, a player who decided not to contribute kept the 2-point endowment The payoffs to a member of Team A as a function of his decision to contribute (C) or not to contribute (NC), the number of ingroup contributors (mA) and the number of out-group contributors (mB), appears in Figure The payoff parameters of the IPD game were such that: First, withholding contribution was the dominant individual strategy; that is, regardless of what the ingroup and out-group members did, the individual earned an extra point by not contributing Second, the dominant strategy for each team was to have all of its members contribute, regardless of what the out-group did In the present experiment, each team player earned more point if all group members (including him) contributed than if they all did not Third, all members of both teams were better off if they all withheld contribution than if they all contributed When no one contributed (a 0:0 tie) each player earned points whereas if all contributed (a 3:3 tie), each player earned only points No-contribution was, in fact, the collectively (i.e., Pareto) efficient outcome of the game, the one which maximize the earnings of all six participants Figure Payoff to a member in team A as a function of the decision to contribute (C) or not to contribute (NC), the number of in-group contributors (mA) and the number of out-group contributors (mB) Payoff C NC 0 0 1 2 2 3 3 3 mA , mB The first and second properties of the IPD game define the intra-group payoff structure as a three-person PD game or a social dilemma (Dawes, 1980) Although the in-group’s payoffs decrease the more out-group players contribute, the structure of the intra-group dilemma remains constant regardless of the number of out-group contributors.2 As can be seen in Figure 1, in all four intra-group PD games (corresponding to 0, 1, and out-group contributors in the IPD game) the cost of contribution for the individual and the benefit (i.e., externality) it produces for the team are the same Therefore, if one assumes that individual behavior is motivated solely by self-interest the assumption of narrow rationality one should expect no contribution in the one-shot IPD game, irrespective of the out-group’s behavior Similarly, if one assumes that individuals are motivated only by a concern for the collective in-group interest, one should expect full contribution, regardless of what the out-group does Of course, in reality, participants are likely to be concerned with both self-interest and common group interest to various degrees Nonetheless, any fixed combination of self-interest and group interest should lead to a constant contribution rate, irrespective of the number of out-group contributors What if participants are predisposed to maximize the relative difference in payoffs between the in-group and the out-group? The assumption that people are motivated to achieve positive self esteem by making the in-group positively distinct from the out-group, is central to social identity theory (Hogg & Abrams, 1988; Tajfel and Turner, 1986) This competitive inter-group motivation was demonstrated in numerous laboratory experiments using the minimal group paradigm (for reviews see Brewer, 1979; Diehl, 1990; Messick & Mackie, 1989; Tajfel, 1982) However, in the IPD game individual behavior, even if governed by a motivation to maximize the groups’ payoff difference, should not be affected by the behavior of out-group members This is so, because in the IPD, individual contribution increases the ingroup’s payoff by points and reduces the out-group’s payoffs by points, regardless of the out-group behavior Therefore, no matter what the out-group does, individuals who wish to maximize the payoff difference between their team and the other team should always contribute Participants’ decisions are expected to be affected by out-group behavior in the one-shot IPD only to extent that they are motivated to “win” or at least not “lose” the game That is, if it is important to them that their group earns more than the out-group (by any margin) or that it earns not less than the out-group The notion that participants are motivated to get at least as much as out-group members (i.e – motivated not to “lose” the game) is supported by studies done in the minimal group paradigm, which showed that equity considerations affect participants’ decisions (Diehl, 1989; Ng, 1981) These studies suggest that part of the reason for biased allocations in the minimal group paradigm is that participants expect biased allocations by out-group members In trying to achieve an equitable allocation participants discriminate against out-group members themselves In the IPD game, which has a symmetric payoff structure, equity considerations dictate that participants would contribute at the level they expect out-group players to contribute.3 Repeated interaction in the IPD game: The repeated IPD game is different from the one-shot game in two important ways: First, in an on-going interaction behavior can be dependent on the earlier choices of other players, whereas in a oneshot game this is not possible This opens the possibility for using strategies of reciprocal cooperation in light of which contribution is seen as a rational strategic move Second, an iterated environment provides players with an opportunity to learn the structure of the strategic situation and adapt their behavior accordingly an opportunity that they not have in a one-shot game Several experiments that examined the dynamics of contribution in the iterated IPD game (Bornstein, Erev & Goren, 1994; Bornstein, Winter & Goren, 1996; Goren & Bornstein, 1999) show that, when communication among players is prohibited (both within and between teams), contribution decreases steadily as the game progresses These works maintain that the gradual decrease in contribution levels is most readily accounted for by individual rationality (i.e., selfishness) To explain this finding all one needs to assume is that players adapt their choice behavior as they become more experienced, so that choices that have led to good outcomes in the past are more likely to be repeated in the future (Harley, 1981; Maynard-Smith, 1984; Selten, 1991) Since withholding contribution is the unconditionally best individual strategy in the IPD game, this simple principle of reinforcement learning, known as the law of effect (Thorndike, 1898), would inevitably move players in the direction of no contribution This interpretation receives substantial support from computer simulations which, using Roth and Erev’s (1995) quantification of the law of effect, closely reproduce the experimental results However, in addition to being the selfish (narrowly rational) individual strategy, withholding contribution is also the cooperative strategy vis-a-vis the other group, since it always increases the total out-group payoff by points (1 point for each individual out-group player) Therefore, low contribution levels could, in principle, reflect an evolution of cooperation between the two teams Research on the two-person prisoner’s dilemma game has shown that mutual cooperation evolves over time (Radlow, 1965; Rapoport, Am & Mowshowitz, 1966; Rapoport, An & Cammah, 1965) Further studies have shown that strategies of reciprocal cooperation, like TIT-FOR-TAT (Axelrod, 1984), are influential in bringing mutual cooperation (Oskamp, 1971; Komorita, Hilty, & Parks, 1991; Wilson, 1971) Reciprocity is defined as a norm that “prescribes that we should help those who have help us in the past and retaliate against those who have injured us” (Komorita, Parks & Hullbert, 1992, p 608) Gouldner (1960) viewed the reciprocity norm as universal and contributing to the stability of social structure It is possible that such tendencies for reciprocation are generalized to intergroup contexts (Patchen, 1987) Rabbie (1998), for instance, explains the typical finding in the Group-Individual Discontinuity paradigm (see review in Insko & Schopler, 1998) as a reciprocity effect According to Rabbie, it is possible that the increase in competitive choices of groups (in comparison to individuals) results from the fact that groups tend to reciprocate exploitative choices more than individuals Using between-team reciprocation in the IPD can help bring about the Pareto efficient outcome of no contribution By reacting to out-group contribution in kind players can deter such behavior of out-group members This is so, because their contribution would reduce the out-group earnings in the round that follows Reacting to out-group contribution in kind is also consistent with the notion that people employ equity considerations in inter-group interactions Even though equity and reciprocity are not identical, the use of reciprocal strategies can reduce the difference between the final outcomes of the two teams In an attempt to differentiate between the process of learning and that of between-team reciprocation in intergroup interaction, Goren and Bornstein (1999) conducted an experiment in which the IPD game was played repeatedly under different matching protocols Their ‘Matching protocol’ manipulations related to changes in the composition and matching of groups from one round to the other during the repeated IPD experiment In the fixed-matching condition, team composition and matching between teams was constant throughout the entire game This condition mimics a naturally occurring intergroup interaction, in which people belong to the same distinct group and two groups repeatedly interact with each other In the mixed-matching condition, the participants were randomly assigned to teams, which were randomly paired for an IPD game at the beginning of each round of the experiment Both matching protocols provided participants with the opportunity to learn the structure of the one-shot IPD game But, whereas the fixed protocol enables them to use between-team reciprocal strategies, the mixed protocol hinders any form of effective reciprocation The results showed no effect of matching condition on contribution, nor an interaction of condition with time, thus failing to support between-group reciprocation The experiment by Goren and Bornstein (1999) constituted a weak test for the between-group-reciprocation hypothesis In their “natural” experimental setting it is quite difficult to disentangle the effect of between-team reciprocation from that of learning If all participants are learning the same thing, namely the dominant strategy of withholding contribution, it is difficult to detect those players who (potentially) make their decision contingent on the behavior of out-group players Reciprocation in this case (to the extent that it occurred in the fixed-matching condition) can possibly alter the speed of the dynamic process but not reverse its direction Given the problem in interpreting the results of Goren and Bornstein (1999), the present experiment used a more direct approach to examine between-group reciprocation Instead of using “real” out-group players, this study used simulated ones Using virtual players, whose behavior is predetermined, enables assessment of the extent to which individuals react to the out-group The virtual out-group players in this study displayed different levels of contribution at different periods of the game Based on the principal of between-group reciprocation it was hypothesized that the contribution levels of the participants’ would be affected by those of the virtual outgroup players Specifically, participants were expected to contribute more following high levels of out-group contribution, and less following low levels of out-group contribution It is important to note that, although learning and reciprocation lead to the same outcome, the two processes assume fundamentally different strategic aims The 10 decreasing The overall high contribution there is influenced by the very high initial levels and not from a flat contribution trend Second, even though significant lagged correlations were not found in all of the conditions one can not claim that participants there did not react to out-group behavior In the ‘Hi-Cont’ conditions, for instance, contribution level remained the same throughout the entire game This pattern is distinctly different from the pattern of contribution in all previous experiments that did not involve manipulation of out-group contribution (Bornstein, Erev & Goren, 1994; Bornstein, Winter & Goren, 1996; Goren & Bornstein, 1999; Goren & Bornstein, 2000) and must have resulted from reacting to out-group behavior A possible explanation for the low lagged correlations is that the virtual outgroup behavior in the present experiment (in both the Hi- and Low-Cont conditions) was considerably less variable than in experiment In particular, participants in the Hi-Cont conditions almost did not experience zero out-group contribution and participants in the Low-Cont conditions almost did not experience full out-group contribution (see table for details) It is possible that this ‘range-truncation’ attenuated the lagged correlations between participants’ decisions and out-group behavior in previous rounds In sum, the observed contribution patterns in experiment gave partial support to the a priori predictions, which were based on the between-team reciprocation hypothesis The interaction effect which was not predicted resulted from high contribution in the ‘Low-Cont’/Hi-Var’ condition The question raised by these results is whether individuals lower contribution only in response to a similar behavior by all out-group members As mentioned earlier, the focus of experiment was not on individuals’ use of between-team reciprocation, but rather on testing whether the perception of out-group 35 members’ motivation is based on their observed behavior Indeed the results here are clearer As in experiment1, participants were very attentive to the out-group’s behavior Participants recalled well the mean contribution level of the out-group In addition to the results of experiment 1, experiment shows that participants accurately remember the contribution behavior of each individual out-group player Experiment also shows that the motivations attributed to out-group members correspond quite well to their actual behavior Out-group members who contributed more were rated as more competitive and as more “patriotic” then those who contributed less This was found on the aggregate level, i.e.- in the mean attributions for all three out-group members, and in the attributions for individual out-group members However, the perception of the cooperative motivation (maximizing joint gains of both teams) was totally uninfluenced by the experimental manipulations No differences were observed in attributing this motivation to out-group members - not at the aggregate level nor at the individual level In line with the hypothesis of betweenteam reciprocation low contribution levels of the out-group led to a decrease in contribution by the participants It was reasonable to expect that this reciprocation of no- contribution would be accompanied by attributing a cooperative motivation to out-group members That this was not the case suggests that participants were focused more on retaliating high levels of out-group contribution than on reciprocating the cooperative choice of no contribution by the out-group In sum, experiment shows, that participants’ perception of out-group behavior is quite accurate and that they attribute corresponding motivations to the members of the out-group both at the aggregate and the individual levels The 36 perception of out-group members’ motivation, however, focused more on competitiveness than on intergroup cooperative motivations The results place some boundary conditions on the notion that intergroup conflict should increase the tendency to see out-group members as similar to one another Indeed, the Judd and Park (1988) study that tried to address this question gave mixed results: lower judgments of out-group variability at the group level (in the competition condition) but better recall for individuating information about out-group members The current data shows that out-group perception can be accurate and varied, at least in aspects that are important to decision making within the intergroup conflict As Messick and Mackie (1989) note, even in situations of extreme intergroup conflict (i.e., war) there might be an incentive to differentiate between out-group members (p 58) General Discussion The approach taken by this study is different from that which typifies the stereotyping literature Instead of focusing on in-group/out-group biases in situations of “minimal” interdependence (e.g., Platow, Mclintock & Liebrand, 1990; Sherman et al 1998), it studies how the behavior of the out-group, in the context of a “realistic” on-going conflict, affects the behavior of the in-group and its perception of the outgroup In terms of Wilder and Simon’s (1998) classification, the focus here is on dynamic groups, groups in interaction, rather then on groups as mere social categories The IPD team game, employed in this study as a model of intergroup conflict, entails conflict of interests within the competing groups as well The intragroup conflict is conceptualized as an n-person PD game, or a social dilemma This conceptualization, which distinguishes between the collective group interest and the 37 interest of the individual group member, implies two qualitatively different processes of conflict resolution, one which involves reciprocal cooperation at the intergroup level, and another that relies on narrow-rationality, or selfishness at the individual level Previous results in iterated play of the IPD (without communication) provided no evidence for between-group reciprocation When players cannot communicate, a decline in contribution was observed as the game progressed (Bornstein, Erev & Goren, 1994; Bornstein, Winter & Goren, 1996) This pattern is consistent with the notion that individuals gradually learn that, personally, they are better off withholding contribution, regardless of what the other (in-group and out-group) players In the two experiments reported here it was found, through direct manipulation of out-group contribution level, that individuals are affected by the out-group’s behavior In other words, some form of between-team reciprocation is taking place, even when group members cannot coordinate their actions This reciprocation, however, is only partial, in the sense that the level of out-group contribution is not quite matched In particular, when there were no out-group contributors on round t, there was typically some in-group contribution in round t+1, and when out-group contribution was larger than zero, in-group contribution was typically less than full These data should be contrasted with recent results of IPD play with communication (Goren & Bornstein, 2000) When group members can communicate and coordinate their action, groups often use reciprocation strategies The reciprocation strategy which seems the most effective in bringing about a “peaceful” resolution to the conflict, is a strict between-team TIT-FOR-TAT strategy, where cooperative (no-contribution) behavior by the out-group is reciprocated in kind, but any positive level of contribution is retaliated against with full force (Goren & 38 Bornstein, 2000) Obviously, without communication (as in the current study) group members are unable to coordinate on a strict between-team reciprocal strategy If participants were not fully reciprocating with the out-group, what else explains their behavior in the game? The results are consistent with the interpretation of participants’ behavior as a mixture of reciprocation and learning When out-group contribution is low enough participants not react to small variations in it, and the main process governing their behavior is the one of gradual adaptive learning Hence the decrease in contribution over time in the Low-Cont conditions of experiment When out-group contribution is high participants react by increasing their own contribution This tendency can prevent the usual trend of a decrease in contribution over time (the Hi-Cont conditions of experiment 2) of even reverse it (experiment 1) The data about the perception of out-group motivations is also consistent with this “dual process” model Generally speaking, the results show that participants are highly aware of what the out-group does They recall the out-group’s behavior accurately both at the outgroup’s aggregate level and at the individual level Participants also attributed higher levels of intergroup competitiveness (max-rel) and “patriotism” (max-ingroup) to outgroup members with high levels of contribution than to those with low levels These attributions are certainly correct within the context of the IPD game structure (as discussed in the introduction) However, participants did not distinguish between high-contributing and lowcontributing out-groups on the max-joint scale Clearly, participants did not interpret low levels of out-group contribution as a cooperative move intended to maximize the outcome of both teams (i.e., max-joint) At the same time they regarded high level of out-group contribution as a sign of competitive and “patriotic” motivations Thus, 39 when encountering a competitive out-group (one with high contribution), participants reacted by increasing their own contribution However, when encountering a low contributing out-group, they did not see it necessarily as cooperative, which perhaps can explain why in-group contribution level in this case was higher than that of the out-group In comparison, teams in the Goren and Bornstein (2000) study, which involved within-team communication, had the insight to signal and reciprocate cooperative intents by entirely eliminating contribution on their part In these cases, group members also attributed high cooperative motivation to out-group members It seems that in the current study the reciprocation strategy that participants employed focused more on retaliating high levels of out-group competition than on reciprocating low levels of out-group contribution (levels which could have been construed as attempts for mutual cooperation between the teams) Much research has shown that groups are highly competitive much more so than individuals under the same structural conditions (Insko &Schopler, 1998) Insko et al (1998) show that this “discontinuity” or group-competitiveness effect can be reduced if groups use long-term considerations Insko et al introduced such considerations as part of their experimental manipulations The present experiments, as well as the experiment by Goren & Bornstein (2000), demonstrate that groups, and to a lesser extent individual group members, are capable of using long-term considerations (or repeated-game strategies) without outside intervention Rabbie (1998) made a similar argument Using a paradigm close to that of Insko and his associates, he shows that groups employ reciprocity considerations more often then individuals Rabbie attributes the use of reciprocal strategies by groups to intragroup discussion He maintains that during discussion group members 40 gain a better understanding of game’s reward structure and, as a result, “groups … are more likely than individuals to follow a long-term cooperative tit-for-tat strategy” (p 485) The results of Goren and Bornstein’s (2000) experiment on the effect of within-group communication in the IPD game are clearly in agreement with Rabbie’s argument The current study suggests that, while intragroup communication is necessary for strict between-group reciprocation, people respond to out-group behavior even without being able to communicate The current line of research on repeated play of the IPD game opens many possibilities for additional study on the conditions that promote cooperation between groups The Goren and Bornstein (2000) study and the different reaction to the two Low-contribution conditions in experiment (the one with high variability and the one with low variability) suggest that people are more likely to reciprocate attempts of cooperation that all out-group members adhere to The data certainly shows that people are perceptive of behavioral differences between out-group members This question certainly merits additional research and points to a functional relation between intergroup reciprocation behavior and the perception of out-group variability One of the problems in analyzing the data of experiment was that apparently there were great individual differences in the willingness to contribute This aspect of interaction in the IPD game was studied by Probst, Carnevale and Triandis (1999) They found that individuals who strongly endorsed values of vertical individualism (characterized by viewing the self as autonomous and accepting social inequality) were also very likely to contribute in the IPD game Individuals who strongly endorsed values of vertical collectivism (characterized by viewing the self as an 41 aspect of the group while accepting inequality) indicated a very low willingness to contribute in the IPD Studying such individual differences can explain initial levels of contribution in the repeated IPD game and help explain more variance of behavior in the game It can probably more than just that A recent study of van Lange (1999) found that individuals who show a pro-social value orientation also show the strongest tendency for reciprocation with another player in a two-person PD game Similarly, it is possible that individual 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Intergroup Cognition and Intergroup Behavior Mahwah, NJ: Lawrence Erlbaum Wilson, W (1971) Reciprocation and other techniques for inducing cooperation in the prisoner’s dilemma Journal of Conflict Resolution, 15, 167-196 47 Footnotes 48 This research was supported by a doctoral research grant from the Israel Foundations Trustees (1997-1998) and was done as part of the requirements for my doctoral thesis Additional support was given by the Joseph Trink Fellowship Endowment Fund (France) I thank Professor Gary Bornstein and three anonymous reviewers for many valuable comments on an earlier version of this paper I also wish to thank Zohar Gilula and Alexey Valenco, of RatioLab (the Laboratory for Interactive Decision Theory at the Hebrew University of Jerusalem), for their help in data collection and in programming the software for the experiments Please address correspondence to Harel Goren, RatioLab Laboratory for Interactive Decision Theory, Faculty of Social Sciences, The Hebrew University of Jerusalem, Mt Scopus, Jerusalem 91905, ISRAEL E-mail: HarelGoren@yahoo.com The absolute level of the payoffs to in-group members decreases, following out-group contribution, because the game between the two teams (considering each team a unitary player) is a 2-person prisoner’s dilemma game as defined by the second and third properties above Of course, in the IPD model and in the classical minimal group paradigm all participants are symmetric - they have equal choices to make with equal power over allocations Therefore it is impossible to distinguish equity considerations from equality considerations in these two paradigms Also note the following: A- each virtual out-group member contributed exactly 30 times in 60 rounds (50%) Therefore, there is zero variability between individual out-group members in their level of contribution and there is no point in assessing differences in the attribution of motivations to specific virtual out-group members B- the exact pattern of contribution over time of the three virtual out-group players within the same condition followed the same pattern (HTL or LTH) Participants’ decisions and all feedback information were handled by a computer program that used the RatImage toolbox (Abbink & Sadrieh, 1995) The prediction for the self-gain motivation is less clear Low levels of contribution are consistent with self gain However, in the context of the repeated game, high levels of contribution can also be motivated by self gain if they are intended to promote long run cooperation within the group Because this experiment did not control the behavior of in-group members it is hard to determine whether there exist tendencies to view out-group members’ motivations as more negative and/or as more similar to each other than in-group motivations The main thrust of this experiment was to test the extent to which observed out-group behavior affects the perception of out-group members’ motivations and to relate these perceptions to the notion of between-team reciprocation In the Low Variability conditions all three virtual out-group players showed the same pattern of contribution over time (increase in the High Contribution condition and decrease in the Low Contribution condition) In the High Variability conditions virtual out-group members showed the corresponding contribution pattern (increase in the Hi-Cont condition and decrease in the Low-Cont condition) while the third virtual player showed a slight opposite trend The absolute deviations of the recalled contribution rates from the actual rates of contribution by the different players were calculated for each participant The three participants with the highest accuracy scores (i.e., with the lowest sum of absolute deviations) were contacted and paid the amount of 35 NIS each 10 I am in debt to one of the anonymous reviewers for suggesting this idea ... (increase in the High Contribution condition and decrease in the Low Contribution condition) In the High Variability conditions virtual out-group members showed the corresponding contribution... manipulating the variability in contribution behavior of individual players within the out-group, in addition to manipulating their average contribution level The literature on inter-group perception. .. contribution by participants in the Hi-Cont conditions then in the Low-Cont conditions However, this effect can be greatly influenced by the initial levels of contribution in the different conditions