The authors have declared that no competing interests exist.
Conceived and designed the experiments: MM JD. Performed the experiments: MM JD. Analyzed the data: MM JD. Contributed reagents/materials/analysis tools: MM JD. Wrote the paper: MM JD.
We developed a new experimental design to test whether or not individuals engage in conflict between social groups because they seek to harm outgroup members. Challenging prominent social psychological theories, we did not find support for such negative social preferences. Nevertheless, subjects heavily engaged in group conflict. Results support the argument that processes that act within social groups motivate engagement in conflict between groups even in the absence of negative social preferences. In particular, we found that “cheap talk” communication between group members fuels conflict. Analyses did not support the notion that the effect of communication results from guilt-aversion processes.
Contributing to the production of public goods is collectively efficient but it is not individually rational. Scholars from various academic disciplines are therefore puzzled by the high contributions to the production of collective goods that have been observed in field research
In an intergroup-conflict setting, the population consists of distinct social groups, each of which faces an intragroup collective good problem. In addition, contributions to the collective good of one’s group create negative externalities for the other group in that they reduce the value of the collective good of the other group. Typical examples of intergroup-conflict settings range from team sports such as soccer, to TV talent shows where fans vote for contestants, to competition for market share between organizations, to election campaigns in which political parties compete for voters, to violent conflicts between nations. In each of these cases, each individual (e.g., each player of a soccer team or each member of a political party) has to decide how much to contribute to the public good of her own group. Contributions produce benefit for all group members but also entail considerable costs for the contributor, rendering contribution individually irrational and creating the intragroup collective-good problem. In addition, contributions to the group’s public good decrease the welfare of others outside the own group: the chances of winning for the competing sports team become slimmer; the market shares of other organizations decrease; the number of votes for the competing political parties decreases; the number of enemy casualties of war increases.
Obviously, rational egoists will not contribute to the collective good of their group and, therefore, will not engage in intergroup conflict. Nevertheless, everyday experience as well as experimental research
Scholars debate which individual motives underlie contributions in intergroup conflict situations. On the one hand, social-identity theory
Empirically identifying the motives that drive contributions to a given intergroup conflict is an intricate problem
There is little empirical research on the motives that underlie contributions to a given intergroup conflict. Halevy et al.
Further doubt on the outgroup-hate mechanism was cast by recent psychological research
Inspired by these empirical findings, we study in this contribution whether individual engagement in intergroup conflict is motivated by negative social preferences towards the outgroup (outgroup hate). To this end, we developed a simple formal model of intergroup conflict that takes into account social preferences towards in- and outgroup members. Analyzing the model, we developed a new experimental design which allows drawing conclusions about the nature of other-regarding preferences. Results of two laboratory experiments that apply this experimental design show that, in the setting of our experiment, contributions to intergroup conflict were not motivated by outgroup hate, a finding that challenges psychological theories of intergroup relations
The absence of outgroup hate, however, does not exclude that individuals heavily engage in conflict with the other group, decreasing their own as well as collective welfare. In contrast, as conjectured by Abbink et al.
In order to test this conjecture, we studied in the second experiment whether intergroup conflict is fueled when we allow subgroup members to engage in cheap-talk communication, a social process that should not affect decisions by rational egoists but that has been shown to increase contributions in public-good experiments
In addition, the second experiment was specifically designed to test why communication increases contributions, a critical question because communication comprises a multitude of social processes
The main purpose of this study was to test whether intergroup settings lead to positive or negative social preferences regarding outgroup members and whether high engagement in intergroup conflict is possible even in the absence of outgroup hate. To this end, we present in the following a game-theoretic model of intergroup settings that takes into account social preferences regarding members of both individuals’ ingroups and outgroups. Based on this model, we identified two experimental conditions which can be compared in order to draw conclusions about the nature of preferences regarding outgroup members.
Two central features characterize intergroup settings. First, individuals are members of one of two distinct social groups of
Second, in intergroup settings individual contributions to one’s group’s public good also affect the material value of the public good of the respective outgroup to a degree that is described by parameter
If parameter
The second condition is characterized by
Modeling individual contribution decisions, we assumed a simple linear ‘altruism model’ where the altruism parameters may adopt different values for members of different groups and are allowed to be negative. To be more precise, individual
A player’s utility function thus has two social preference parameters
In the following, we first focus on model predictions for a one-shot stage game under Harmony and Conflict. Subsequently, we turn to infinitely repeated games and compare the ‘trigger strategy’ Nash equilibria as functions of the players’ social preferences for ingroup and outgroup members.
Given the game and the assumptions outlined above, we can analyze the one-shot stage game. In Harmony, the marginal utility of contributing to the group’s public good is
Repeating the stage game indefinitely allows for the existence of Nash equilibria other than the ‘no contribution’ strategy profile in the one-shot stage game. Throughout we assume that players discount future payoffs by a constant discount parameter
First consider the contribution profile where all players across both groups contribute a nonzero part of the endowment (
The utilities in each round of the Contribution Phase are
Consider the contribution profile where all players who belong to the ingroup contribute
Let
The maximum utility a player can get in a single round by deviating is obtained when she contributes nothing to the group public good, while her fellow ingroup members continue contributing
Performing the same analysis for Conflict, we find that the utility in each round of the Contribution Phase is
By
The equilibrium analysis of the ingroup symmetric trigger strategy profile thus yields two threshold values for the discount parameter,
Summarizing the theoretical results for our experimental games, we have found an ingroup symmetric strategy profile that allows strictly positive contributions in both Harmony and Conflict, while not contributing anything is the unique dominant strategy in the one-shot stage game. In addition, under the current model and equilibrium profile we can formulate the following corollary. This conclusion is valid even if ingroup social preferences (
In our experimental study we draw a simple random sample of participants. Therefore, there are no differences in the expected distributions of the discount parameter between the Harmony and the Conflict condition. This implies that the likelihood of any within-group contribution level
In behavioral terms this means the following. We first of all assume that players condition their contributions only on the contributions made by their fellow ingroup members, not on those made by outgroup members. Secondly, players are assumed to have a time preference, embodied in their discount parameter. We then showed that the critical discount parameter threshold that makes nonzero contributions sustainable in equilibrium is smaller in Harmony than in Conflict, unless players negatively value payoffs for outgroup members. In other words, any contribution level that can be sustained in equilibrium in Conflict, can be sustained in Harmony, but the reverse is not true. Thus, under the current model, contributions in Conflict will be larger than those in Harmony only in the presence of “outgroup hate”. Thus, comparing empirical contributions in Harmony and Conflict allows drawing conclusions about whether contributions are motivated by negative social preferences towards outgroup members.
Two potentially problematic aspects of the model were taken into account in the design of the experiment. First, in order to be able to apply the infinite horizon model to a laboratory setting where subjects play a fixed number of periods, we did not inform subjects about the number of periods they were playing. Second, the model is based on an ‘ingroup trigger strategy’, in which only an ingroup contribution level
We make the following observation concerning the comparison of our experimental design with that of Halevy et al.
Comparing our design with that of Abbink et al.
Both experiments were conducted at the Sociological Laboratory of the Department of Sociology at the University of Groningen in the Netherlands. Subjects were recruited from the subject pool of the Department of Sociology, which comprises mainly students and alumni from the two universities in Groningen. Volunteers registered for experimental sessions, using an online form
The recruitment and the experiment complied with the ethical guidelines set out by the Sociological Laboratory of the Department of Sociology at the University of Groningen (
The aim of the first experiment was to empirically test whether or not negative social preferences towards outgroup members motivate contributions to intergroup conflict, applying the new experimental design. The experiment consisted of two sets of treatments. In the first set, subjects were assigned to one of two treatments, allowing a within and between subjects comparison between the Harmony and the Conflict condition. In the “first Conflict, then Harmony treatment”, subjects first made 10 decisions under the Conflict condition (
The second treatment set of the experiment provided two baseline conditions. In the first baseline condition, contributions to the public good of a group had no effect on the other group (
Treatment | Treatmentset | Condition(parameter |
Information about out-groupcontributions provided | Number ofsubjects |
1 | 1 | first Conflict ( |
yes | 36 |
then Harmony ( |
||||
2 | first Harmony ( |
yes | 48 | |
then Conflict ( |
||||
3 | 2 | 20 rounds of Public | yes | 48 |
Good game ( |
||||
4 | 20 rounds of Public | no | 36 | |
Good game ( |
For each of the four treatments, we scheduled four experimental sessions with 12 subjects each. There were two societies in each session and each society consisted of two subgroups of three members (see
This was the first experiment on intergroup games that had been conducted with members of this subject pool. We therefore expected that subjects did not have experiences with this type of experiment. The experiment was conducted in English language, in order to make sure that both Dutch and foreign participants had an equal understanding of the instructions.
Sessions began with general verbal instructions. Next, subjects read detailed instructions on the computer screens, receiving all instructions that concerned the public good game of their own group. In the conditions where subjects were informed about their outgroup, subjects read on the next screen that there was a second group and how this group affected their payoffs. Next, subjects interacted in 20 periods. In the first treatment set (Harmony and Conflict), subjects read after the tenth period how the rules of the game were about to be changed and then continued in the respective other condition. Subjects were not informed about the number of periods that they played in each condition.
Each interaction period consisted of four steps. First, subjects received 10 points (each worth 2 Euro cents) and decided how many points they would like to contribute. In order to assess subjects’ expectations about the contributions of their group members, subjects were asked in the second step to guess how many points the other two members of their own group had just contributed on average. In order to increase the validity of this measure
Figures S1, S2, and S3 in
Dependent variable: Contribution | ||||
Empty model | Main effects | Full model | Final model | |
Constant | 5.92 |
5. 55 |
5.38 |
5.53 |
(0.35) | (0.54) | (0.56) | (0.36) | |
Harmony | 78 |
95 |
78 |
|
condition | (0.13) | (0.19) | (0.13) | |
First Harmony | −0.04 | 0.11 | ||
then Conflict | (0.71) | (0.73) | ||
Interaction | (0.30) | |||
effect | (0.26) | |||
Between | 2.87 | 2.87 | 2.87 | 2.87 |
subgroup var. | (0.94) | (0.94) | (0.94) | (0.94) |
Between | 1.52 | 1.53 | 1.53 | 1.53 |
subject var. | (0.35) | (0.35) | (0.35) | (0.35) |
Residual | 6.97 | 6.81 | 6.81 | 6.81 |
variance | (0.25) | (0.24) | (0.24) | (0.24) |
−2 loglikelihood | 8218.83 | 8181.95 | 8180.60 | 8181.95 |
Number of subjects | 84 | 84 | 84 | 84 |
Number of decisions | 1680 | 1680 | 1680 | 1680 |
Standard errors in parentheses.
***significantly different from 0 at the 1 percent level (twosided Wald-test).
**significantly different from 0 at the 5 percent level (twosided Wald-test).
*significantly different from 0 at the 10 percent level (twosided Wald-test).
Dependent variable: Contribution | ||
Empty model | Full model | |
Constant (mean std. | 6.33 |
7.02 |
PGG in full model) | (0.31) | (0.64) |
a = 0 (PGG with | −0.44 | |
two groups) | (0.85) | |
Harmony (a = 1.5) | −0.79 | |
(0.85) | ||
Conflict (a = −1.5) | −1.55 |
|
(0.91) | ||
between subgroup | 4.38 | 4.09 |
variance | (0.99) | (0.94) |
between subject | 2.15 | 2.15 |
variance | (0.35) | (0.35) |
Residual variance | 4.38 | 4.38 |
(0.16) | (0.16) | |
−2 loglikelihood | 7648.05 | 7644.96 |
Number of subjects | 168 | 168 |
Number of decisions | 1680 | 1680 |
Standard errors in parentheses.
***significantly different from 0 at the 1 percent level (twosided Wald-test).
**significantly different from 0 at the 5 percent level (twosided Wald-test).
*significantly different from 0 at the 10 percent level (twosided Wald-test).
In sum, we found that subjects contributed significantly more in the Harmony than in the Conflict condition. According to the Corollary we can, thus, conclude that Experiment 1 did not provide evidence for negative social preferences towards the members of the outgroup. Likewise, the comparison with the baseline conditions did not provide evidence for positive social preferences towards members of the outgroup.
Dependent variable: Contribution | |||
Harmony( |
Conflict( |
||
Constant | 0.99 |
0.96 |
0.06 |
(0.50) | (0.45) | (0.52) | |
Expected contribution | 0.80 |
0.84 |
0.89 |
ingroup members | (0.06) | (0.07) | (0.07) |
Expected contribution | 0.08 | 0.03 | 0.08 |
outgroup members | (0.05) | (0.07) | (0.08) |
between subject | 2.80 | 2.96 | 1.53 |
variance | (0.62) | (0.66) | (0.35) |
Residual variance | 2.29 | 2.70 | 6.81 |
(0.16) | (0.18) | (0.24) | |
−2 loglikelihood | 1883.59 | 1957.44 | 1620.05 |
Number of subjects | 48 | 48 | 36 |
Number of decisions | 480 | 480 | 360 |
Standard errors in parentheses.
***significantly different from 0 at the 1 percent level (twosided Wald-test).
**significantly different from 0 at the 5 percent level (twosided Wald-test).
*significantly different from 0 at the 10 percent level (twosided Wald-test).
If, contrary to our assumption, subjects in the Conflict condition sought to increase payoff differences between their ingroup and members of the outgroup as social psychological theories suggest
All analyses in
We found that in all three conditions contributions were significantly influenced by the expectations about ingroup members’ contributions. In other words, subjects contributed more points when they expected their group members to contribute many points. In a model (not shown here) of the data from all three conditions we did not find significant differences in the effect size of ingroup expectations.
Importantly, this effect was not found for the expectations concerning the outgroup. In neither of the three conditions, did subjects contribute more or less depending on their expectations concerning the contributions made by the outgroup. This is most surprising for the Harmony condition, because contributions of both in- and outgroup members increased subjects’ own payoffs. Nevertheless, categorizing subjects into two groups appeared to have affected subjects’ decisions in the sense that they paid attention only to ingroup contributions when making their own contribution decisions
In a nutshell, we found contributions in the Harmony condition to be significantly higher than in the Conflict condition. Furthermore, contributions in both Harmony and Conflict turned out to be lower than in the baseline conditions, suggesting that the difference between contributions in Harmony and Conflict were not caused by additional incentives to contribute in Harmony. Finally, we found support for our assumption that subjects based their own decisions on expected contributions by ingroup members only. On the whole, these findings do not provide any evidence for negative social preferences towards the outgroup. In other words, in the setting of this experiment, we did not find support for the outgroup-hate argument. Furthermore, the results suggest that subjects did not seek to increase outgroup members’ payoffs. However, subjects refrained from engaging in behavior that would harm outgroup members, which explains why we found higher contributions in the Harmony conditions than in the Conflict condition.
Results of Experiment 1 did not provide support for the outgroup-hate argument, suggesting that in the setting of this experiment subjects did not seek to increases payoff differences between members of their own group and the outgroup. Nevertheless, we found high contributions in the Conflict condition (5.53 points on average, see
We focused in our second experiment on an alternative intragroup process, communication between group members. Many experimental studies conducted by social psychologists have demonstrated that communication has a striking potential to increase cooperation in collective-good dilemma games
The evidence that psychological research provided for the effects of communication on contributions is impressive. However, in the majority of communication experiments subjects met in a separate room and openly discussed the decision problem before they decided about their actual contributions. This communication process is extremely complex, creating a black box
Recently, economists developed rigorous models of communication in games, focusing on the statement of intentions during communication
The effects of communicating intentions on contributions has been attributed to guilt aversion, the tendency to avoid the psychological costs of letting others down
In Experiment 2, we studied three communication conditions. First, there was a control condition without communication. Second, in the “standardized-messages condition”, subjects informed their group members about their intentions before they entered their actual decision. The purpose of including this condition was to test whether informing group members about one’s intentions and being informed about their intentions does indeed increase contributions, as the guilt-aversion argument suggests.
However, the communication of intentions is only one aspect of communication and it is questionable whether it is the crucial aspect that is responsible for the overall effect of communication on contributions. We therefore added a third condition where communication was not restricted to informing each other about intentions. However, we refrained from allowing the open face-to-face pregame discussions which many psychological experiments are based on
Thus, communication in the condition with short messages was rather complex. However, the communication of short messages excludes nonverbal communication which is very difficult to measure or control experimentally
To our knowledge, there is very little research on intergroup games that involved communication and tested for negative social preferences towards outgroups
For each of the six treatments, we conducted two sessions with 12 subjects each. In total, 144 subjects participated in this experiment. Experimental sessions were randomly assigned to the six treatments. Nineteen participants (13.2 percent) of Experiment 2 had participated earlier in Experiment 1 and were, thus, familiar with intergroup games. The other participants had never taken part in an experiment with an intergroup game before. Subjects were free to subscribe to any session in which they wanted to participate. By chance this produced a pattern in which the 19 subjects that had participated in Experiment 1 were evenly distributed over the six experimental treatments of Experiment 2.
The design of this experiment was similar to the design of the first experiment. There were, however, three main differences. First, in order to keep the duration of experimental sessions below 30 minutes, subjects made only ten decisions instead of twenty. For the same reason, subjects did not enter their expectations concerning the contributions of other participants. Finally, the experiment was conducted in Dutch language, in order to make sure that subjects could formulate and understand the short messages. In the invitation e-mails that were sent to the members of the subject pool, we made explicit that the experiment was to be conducted in Dutch.
In the treatments without communication, each interaction period consisted of two steps. First, subjects entered their contribution and, second, subjects were informed about the individual decisions of their ingroup’s members and the sum of contributions of the other group.
In the conditions with communication, interaction periods also consisted of these two steps. However, there were two additional steps at the beginning of each period. In the standardized-message conditions, subjects were first asked to send a message to their fellow group members by completing the following sentence: “I will contribute
The core results of the second experiment are summarized in
Dependent variable: Contribution | |||
Empty model | Main effects | Full model | |
Constant | 7.54 |
5.81 |
5.86 |
(0.31) | (0.48) | (0.59) | |
Harmony | 0.84 |
0.75 | |
(0.48) | (0.83) | ||
Standardized message | 0.87 | 0.72 | |
(0.59) | (0.83) | ||
Short message | 3.05 |
3.07 |
|
(0.59) | (0.83) | ||
Harmony |
0.31 | ||
message | (1.17) | ||
Harmony |
−0.03 | ||
message | (1.17) | ||
between subgroup | 4.18 | 2.35 | 2.35 |
variance | (0.94) | (0.56) | (0.56) |
between subject | 0.58 | 0.58 | 0.58 |
variance | (0.17) | (0.17) | (0.17) |
Residual variance | 6.09 | 6.09 | 6.09 |
(0.24) | (0.24) | (0.24) | |
−2 loglikelihood | 6900. 85 | 6876.39 | 6876.29 |
Number of subjects | 144 | 144 | 144 |
Number of decisions | 1440 | 1440 | 1440 |
Standard errors in parentheses.
***significantly different from 0 at the 1 percent level (twosided Wald-test).
**significantly different from 0 at the 5 percent level (twosided Wald-test).
*significantly different from 0 at the 10 percent level (twosided Wald-test).
The first important result is that in all three communication conditions contributions were significantly higher in the Harmony condition than in the Conflict condition. On average, subjects contributed 0.84 points more in Harmony than in Conflict. The “Full model” in
In the light of this finding, the very high contributions in the condition where subjects communicated short messages are remarkable. In the Conflict condition with short messages, subjects contributed on average 8.93 of the 10 points that they received in each period. Thus, even though there is no evidence for outgroup hate, subjects contributed most of their points and, thus, fueled the intergroup conflict.
Comparing contributions in the Conflict treatments without communication and the Conflict treatment with short-messages reveals that the very high contributions in the Conflict condition with short messages were caused by the communication. To be more precise, subjects contributed on average 3.05 points more when they could transmit short messages. This supports the claim that intergroup conflicts do not always result from negative feelings towards the outgroup but can be the result of an intragroup process.
Why did the communication of intentions fail to significantly increase contributions? We did find that subjects’ decisions were correlated to their own stated intentions and those of the other group members. For the conditions where subjects transmitted standardized messages,
Dependent variable: Contribution | ||||||
OnlyHarmony | OnlyConflict | Maineffects | Main andinteractions | Finalmodel | ||
Constant | 5.13 |
0.01 | 0.88 | −0.07 | 0.38 | |
(1.90) | (0.94) | (0.96) | (1.15) | (0.70) | ||
Own intention | 0.27 |
0.78 |
0.60 |
0.76 |
0.76 |
|
(0.10) | (0.05) | (0.05) | (0.05) | (0.06) | ||
Higher intention | 0.00 | 0.04 | 0.11 | 0.06 | ||
group members | (0.18) | (0.11) | (0.10) | (0.12) | ||
Lower intention | 0.16 | 0.23 |
0.19 |
0.23 |
0.23 |
|
group members | (0.10) | (0.05) | (0.05) | (0.06) | (0. 04) | |
Period effect | −0.21 |
−0.23 |
−0.22 |
−0.23 |
−0.22 |
|
(0.06) | (0.05) | (0.04) | (0.05) | (0.04) | ||
Harmony | 0.00 | 4.68 |
4.56 |
|||
condition | (0.50) | (2.07) | (1.06) | |||
Own intention | −0.52 |
−0.53 |
||||
(0.11) | (0.10) | |||||
Higher intention | −0.01 | |||||
group member | (0.21) | |||||
Lower intention | −0.03 | |||||
group member | (0.11) | |||||
Period |
0.02 | |||||
(0.07) | ||||||
betw. subgroup | 2.22 | 0.01 | 0.71 | 1.04 | 0.99 | |
variance | (1.25) | (0.28) | (0.36) | (0.51) | (0.49) | |
between subject | 0.20 | 0.93 | 0.26 | 0.59 | 0.61 | |
variance | (0.30) | (0.48) | (0.21) | (0.28) | (0.28) | |
Residual | 6.16 | 4.26 | 5.67 | 5.20 | 5.21 | |
variance | (0.59) | (0.41) | (0.39) | (0.35) | (0.35) | |
−2 loglikelihood | 1141.96 | 1056.86 | 2233.27 | 2211.65 | 2212.10 | |
Number of subjects | 24 | 24 | 48 | 48 | 48 | |
Number of decisions | 240 | 240 | 480 | 480 | 480 |
Standard errors in parentheses.
***significantly different from 0 at the 1 percent level (twosided Wald-test).
**significantly different from 0 at the 5 percent level (twosided Wald-test).
*significantly different from 0 at the 10 percent level (twosided Wald-test).
In other words, subjects’ stated intentions were more reliable in the Conflict than in Harmony condition. It remains an open question what mechanism caused this effect. On the one hand, it could be that in the Conflict treatment subjects took the statement of their intentions more seriously, and thus adjusted their final decisions less than subjects in the Harmony treatment. Alternatively, subjects who were assigned to the Conflict conditions might have felt more morally obliged to stick to their stated intention when they made their decision
Subjects were also influenced by the standardized messages that they received from their group members. However, it turned out that in both conditions subjects hardly considered the message that contained the higher intention and were mainly influenced by the lower intention. The former is demonstrated by the very weak and insignificant effects of the stated intention of the group member with the higher intention in the two separate models for Harmony and Conflict in
Finally, we included period effects in the models of
In a nutshell, analyses of the standardized messages revealed that subjects tended to contribute more points when their group members stated that they would contribute more. We found this pattern in both conditions, concluding that subjects did prefer fair payoff distributions amongst the members of their group. However, subjects adjusted their contributions mainly in accordance with the group member that stated the lower intention and, actually, contributed on average even fewer points than stated by the lower intention. This might explain why having the opportunity to transmit standardized statements did not increase contributions substantially.
The analyses of the previous section demonstrated that the statement of the intentions did not increase contributions significantly, failing to support the claim that the communication of intentions is the core process that explains why communication increases engagement in intergroup conflict. Thus, it remains an open question why intragroup communication in terms of short-message communication increased contributions and fueled intergroup conflict. In order to explore which processes might explain this effect, we analyzed the content of the short messages.
Obviously, short messages can contain a multitude of different pieces of information and arguments that might motivate individual contributions. In order to explore the content of the messages and whether receiving messages with a specific content affected subjects’ contributions, we asked three coders to independently from each other evaluate each of the 480 short messages that subjects had transmitted. This method is becoming a standard approach to study the content of communication in economic experiments
Aspect | Coder instruction(short form) | Example of shortmessage (translated) | Cronbach’sAlpha |
Statement of intentions | Does the sender of the messageexplicitly state howmany points he/she isgoing to contribute? | “I will contribute 10 points.” | .709 |
Sending of norms | Does the sender of the message statehow much he/she wantsthe others to contribute? | “I will contribute 10 points again.I hope you’ll do the same.” | .583 |
Persuasion | Does the sender seekto convince the others,using an argument? | “The best is to contribute everything,also in order to seehow the others will react” | .827 |
Perceived groupcompetition | Does the messagemention the other group? | “Nice. Our strategy begins to work out.Keep it up, then Greenwill have less.” | .960 |
Loss aversion | Does the sender raise concerns thathigh contributions are theonly way to prevent losses? | “We have to contribute the maximum.Otherwise we will get negative points” | .810 |
Verbalpunishment | Does sender complain aboutlow contributions of others? | “Stealing 5 cents from us, person whocontributed 7 :P I will have to buy bread.” | .798 |
Positive reinforcement | Does the sender supportthe others in their previous behavior? | “Well done team :)Go ahead with 10 points!” | .662 |
Communication createsgroup identification | Does sender refer to agroup identity/team work? | “Team Blue rules!”(not translated) | .955 |
For each message and each potential mechanism we calculated the average rating across the three coders, arriving at outcome measures that vary between zero and one. A value of zero is adopted if none of the coders thought that the content of the message indicates that the respective mechanism played a role. The outcome measures adopt the value 1 if all three coders consistently answered the coding question with “yes”.
Finally, we tested whether subjects’ contribution decisions were affected by the content of the short messages that their subgroup members had transmitted. Therefore, we calculated for each contribution decision and each potential mechanism the average rating of the two messages that the two subgroup members had transmitted before the decision. These measures were entered as independent variables in random-intercept models with contributions as dependent variable (see
Dependent variable: Contribution | ||||
Model 1 | Model 2 | Model 3 | Model 4 | |
Constant | 8.93 |
8.78 |
8.81 |
8.05 |
(0.16) | (0.22) | (0.15) | (0.43) | |
Harmony | 0.71 |
0.62 |
0.62 |
0.60 |
condition | (0.22) | (0.23) | (0.21) | (0.19) |
Statement of | 0.03 | |||
intention | (0.41) | |||
Sending a norm | −0.16 | |||
(0.41) | ||||
Persuasion | −0.16 | |||
(0.42) | ||||
Group | 0.17 | |||
competition | (0.34) | |||
Loss prevention | 0.39 | |||
(0.76) | ||||
Verbal | 1.45 | |||
punishment | (1.42) | |||
Positive | 1.13 |
1.11 |
0.74 |
|
reinforcement | (0.45) | (0.42) | (0.41) | |
Group identity | 0.77 | |||
(0.65) | ||||
Contribution | 0.10 |
|||
previous period | (0.05) | |||
between subject | 0.24 | 0.21 | 0.19 | 0.04 |
variance | (0.12) | (0.11) | (0.11) | (0.06) |
Residual | 3.39 | 3.34 | 3.37 | 3.27 |
variance | (0.23) | (0.23) | (0.23) | (0.23) |
−2 loglikelihood | 1973.73 | 1963.62 | 1966.84 | 1935.90 |
Number of subjects | 48 | 48 | 48 | 48 |
Number of decisions | 480 | 480 | 480 | 432 |
Standard errors in parentheses.
***significantly different from 0 at the 1 percent level (twosided Wald-test).
**significantly different from 0 at the 5 percent level (twosided Wald-test).
*significantly different from 0 at the 10 percent level (twosided Wald-test).
In a nutshell, we found that subjects who received positive feedback contributed significantly more points. On the one hand, this suggests that positive reinforcement might explain the effect of communication on contributions. On the other hand,
Strikingly, our explorative analysis did not provide evidence in support of the remaining mechanisms. Even though subjects frequently stated intentions, formulated norms, tried to persuade, and referred to the other group, contribution decisions turned out to be unaffected by these messages. However, this does not rule out that some of the mechanisms played a considerable role. For instance, it has been argued that group identities form unconsciously
What have our studies taught us about social preferences and intergroup conflict? First, Experiment 1 demonstrated that intergroup settings do not necessarily generate negative social preferences towards members of the outgroup and do not always motivate individuals to harm outgroup members. This result is consistent with findings from earlier game theoretic research
To be sure, the lack of support for outgroup hate in our experiments does not exclude that outgroup hate might play a critical role in other intergroup settings and can motivate contributions to conflict. However, our results show that individuals may engage in intergroup conflict without feelings of outgroup hate. This is an important finding because it can not be explained with classical theories of intergroup relations
Likewise, our results do not exclude that a minimal group categorization might create ingroup love in the sense that subjects have positive social preferences towards members of the ingroup, an effect which found support in recent game theoretic experiments
Our second experiment provided new support for the striking claim that populations can suffer from intergroup conflict even though individuals do not seek to harm outgroup members because processes that act within subgroups motivate high contributions and fuel intergroup conflicts
Extending earlier studies, we sought to identify the mechanism that underlies this communication effect, trying to open the black box of communication research that has been criticized earlier
In sum, it remains an open question why communication in terms of short messages increased contributions and fueled intergroup conflict. Our explorative analyses of the content of messages provided some support for the argument that group members tend to praise high contributions of group members and, thus, provide selective social incentives to contribute. However, statistical effects were rather small, suggesting that this mechanism accounts only for parts of the communication effect. Nevertheless, future research might take this finding as a starting point and conduct an experiment where subjects can send standardized feedback messages to their group members.
Identifying the mechanisms that cause communication effects is an intricate problem, because multiple mechanisms might interact and add up to the overall effect of communication. Nevertheless, the apparent contradiction between the theoretical insight that contributions to intergroup conflict are neither individually rational nor collectively efficient, on the one hand, and the high contributions that experimenters observed when subjects could communicate, on the other hand, makes it an important endeavor for future research.
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We thank Johannes Ackva, Welmoet de Ruijter, and Jaap Oude Mulders for their help.