Mobs rule in the economics laboratory

Bullying and victimisation are difficult subjects to study in the real world, because much of the time, the actions are hidden. Victims may be reluctant to speak out due to fear, and perpetrators are certainly not going to admit to their actions. One solution is to test theories in an experimental setting, as this recent article by Klaus Abbink (Monash University) and Gönül Dogan (University of Cologne), published in the journal Games and Economic Behavior (ungated earlier version here) does.

Abbink and Dogan investigate how mobs form, and how they choose their victims. They ran 42 experimental sessions in Amsterdam and Cologne involving 860 research participants, using a new experiment that they termed the 'mobbing game':

In a group of four players, each player can, but is not forced to, nominate a victim among the group members. If players nominate different individuals or no one, then there is no victim, and players receive their default payoffs. If all other players nominate the same individual, then this individual becomes the victim, his payoff is taken away and the bullies... receive an additional payoff.

So, if three of the players in a group can coordinate on choosing a fourth player, the 'victim' loses their payoff and the 'bullies' are rewarded. The game is played in a repeated fashion 20 times (with different variations I'll discuss below), which allows the players to coordinate (should they choose to do so). Abbink and Dogan ran several variants of the experiment. In the first set of variants, some groups had a high payoff to mobbing, others a medium payoff, a minimal payoff, or no gain at all. They found that:

...mobs become more frequent the higher the individual gains from it are. The overall frequencies of successful mobbing are 74.1% in High, 45.0% in Medium, 16.6% in Low, and 6.3% in No Gain.

Unsurprisingly, when there are greater gains to be had from mobbing, there is more mobbing. It didn't take long for groups to coordinate on finding a victim either:

If we look at the groups in which a victim existed for at least three periods... we see that it took on average 3.5, 4.7 and 6.3 periods in the High, Medium and Low treatments, respectively.

Generally, if in one round of the game two players chose the same other player, the third player would join them in the following round. So, most of the time, mobbing occurred quickly and was persistent. Abbink and Dogan note that this behaviour is in contrast with the idea that subjects believe in fairness and equity. In fact:

In the High treatment, it could be a sensible group behaviour to rotate the victim’s role. This would capture the efficiency gain without victimising a particular individual. However, we hardly observe any such behaviour. Thirteen out of 17 groups in this treatment coordinated on the same victim at least half of the time.

Abbink and Dogan then turn to the question of why mobbing occurs. Do players engage in mobbing because they fear that if they didn't, they would become the next victim? To do this, they designate one of the four players as 'safe' from being a victim. If a player is safe, they should not be afraid of becoming a victim, and if fear is playing a role in mobbing, then mobbing should be less frequent when one player is safe (because it takes all three players to coordinate on a victim for mobbing to be successful). They find that:

The inclusion of a safe player who cannot be mobbed does not reduce the mobbing rate even when the group size, and hence, the required number of bullies for a successful mob is higher. Moreover, safe players nominate more often and are more likely to be part of a mob, implying that impunity increases greed.

Clearly it's not fear of becoming the victim that causes mobbing, if safe players are more likely to nominate another player. Abbink and Dogan next look at how the players coordinate on choosing a victim - who gets chosen? It turns out that anything that marks a player out as different is effective as a coordinating device. Making one player richer than the others causes that player to be more likely to become the victim, but so does making one player poorer than the others. However:

While the fraction of focal victims is very similar in both treatments, the relative payoff of the focal player affects mobbing frequencies only if the focal player is richer. Overall rates are similar in the Medium and Poor treatments (45.0% versus 48.6%, not statistically significant), but if the focal player is richer, mob formation rate rises to 71.1%... Envy towards the richer player increases mobbing rates, while pity towards the poor seems to play no role.

They then dig into this a bit further, by making a second player a focal point by giving them a different colour than the others, as well as having one player be poorer than the others. They now find that:

...group membership indeed plays a role in picking a victim: Subjects are less likely to pick an ingroup member, even when the outgroup victim is poorer. Pity towards the poor does not play a role in mobbing decisions, the poor player instead serves as a coordination device. Further, both payoff difference and colour difference serve as strong coordination devices; players who are different in either dimension are substantially more likely to be chosen as victims than the rest.

Overall across all of their experiments, they conclude that:
...the picture that emerges is that greed is the main driver of mobbing. Subjects themselves confirm this, as an analysis of the questionnaire data shows... There is no evidence for fear or pity playing a role in mob outcomes, and standing out makes one substantially more likely to be a victim.

This is an excellent and interesting paper, although Alex Tabarrok at Marginal Revolution also labelled the results "horrific" and that probably isn't far wrong either. As with all experimental studies, it requires replication though before we can fully accept the results.

[HT: Marginal Revolution, back in November 2018]