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12 January 2022 Kristian Lozina, Presse- und Öffentlichkeitsarbeit, JMU Würzburg

In the court of public opinion, there are few occasions when violence can be justified, but one stands out: revenge against an aggressor. However, in a series of connected experiments Professor Dr Andreas Eder and Vanessa Mitschke, of the Julius Maximilian University of Würzburg, Germany, have illuminated a rather uncomfortable fact about human behaviour and the motivation behind aggressive acts of revenge: while delivering justice may be the intent of retaliation, victim reaction in avenging an aggressor is not without a certain sense of enjoyment.

Revenge may be a popular narrative in cinematic thrillers, but the human psychology behind any act of aggression associated with revenge is a far more compelling story. Psychologists are especially drawn to how revenge seekers moralise their actions; and what goes on in their minds immediately before, and after, experiencing revenge. A great deal of research into this area uses self-report measures to assess attitudes to reported events of revenge aggression. However, little has been done to measure how revenge-takers react to the outcomes of their actions on an offender, and what, if anything, might make them adjust their actions. This is what Professor Andreas Eder and Vanessa Mitschke have set out to investigate.

In a series of studies using a computer-based competitive reaction-time game, against fictitious opponents connected via the internet, participants were exposed to bursts of loud noise when losing a round of the game against an opponent who determined the level of the noise ‘punishment’. Importantly, the participants could watch their ‘opponents’ and their reactions when the participant won a round and could exact revenge in the same way, at a noise level of their choosing.

In their first study, Eder and Mitschke, in conjunction with Professor Mario Gollwitzer, observed the retaliatory behaviour of participants exposed to punishment by seemingly aggressive opponents, and how the participants reacted when they saw the outcomes of their revenge. Participants responded differently when shown video footage of the opponent displaying either pain, sadness, anger, or indifference to the loud noise. A meta-analysis showed that seeing the opponent in pain increased the likelihood that the participant would reduce the level of the punishment in the next round. This suggested a degree of appeasement in their act of retaliation. On the other hand, if instead of pain the opponent displayed sadness, anger, or indifference, it didn’t seem to appease the participants – they didn’t lower the level of retaliatory noise for the next round. This suggested that seeing pain in the face of a former aggressor could put the brakes on any act of revenge.


This research prompted further questioning about what emotions were associated with the reduction in the punishment: Could it be a feeling of satisfaction having avenged a prior misdeed? Or, did seeing the opponent in pain elicit some form of compassion or guilt in the mind of the avenger?

In a series of similar experiments by Eder and Mitschke, participants’ involuntary facial expressions were recorded while they played the competitive reactiontime game, specifically at the point when they punished their opponent. Using electrodes, they measured muscle activation of the eyebrow (corrugator supercilia) whereby furrowing indicates an unpleasant reaction; activation of the corners of the mouth, or smiling (zygomaticus major), and activation of the eye (orbicularis oculi), which indicates a pleasant reaction.

Results of the physiological reactions indicated a pleasant reaction when participants saw a provocative opponent (ie, one who had administered harsh punishment when the participant lost) experiencing pain from their punishment. This suggested the participants drew some measure of enjoyment in exacting revenge. There was little joy shown when punishing either non-provocative opponents, or provocative opponents who showed sadness when punished.


Studies have shown that while some people consider retaliation against transgressors in reported events (such as the killing of Osama bin Laden) satisfactory, others are forced to revisit the original transgression (eg, the 9/11 attacks), which is an overall negative experience. The result: revenge can be ‘bittersweet’. Eder and Mitschke hypothesised that if revenge really is bittersweet, then following a vengeful act there will be a brief sweet reaction, before a longer bitter reaction, when the avenger reflects on the original transgression.

In order to test this idea of an initial sweet reaction, Eder and Mitschke asked participants to rate how pleasant they found Chinese characters after they had been playing two computer games: The first was a reaction-time game including two other players, which involved nominating someone, or being nominated, to be blasted with a loud noise. A crucial part of this game was that one of the players would pick on the participant by always nominating them. In the second game participants were given the opportunity to punish the players from the first game. So, if participants were out for revenge then presumably they would always punish the player that was picking on them. However, unbeknownst to the participant, the computer was actually making the punishment decisions for them and would punish the two other players randomly.

The researchers found that participants were more likely to rate the Chinese character positively after they had punished the player who had been picking on them, than the other player. Interestingly, however, they found that this was only the case for ‘revenge-seeking’ participants, ie, those who chose to inflict punishment on the player that was picking on them more often. So, their results suggest that revenge-seekers do feel more positive after taking revenge. A follow-up study confirmed these findings, but also showed that revengeseekers showed an even more positive response when no-one was punished at all. The authors conclude that revenge ‘is neither wholly sweet nor wholly bitter’ – people generally feel bad after punishing someone, but they can also experience a certain amount of pleasure in this when taking revenge.

Eder and Mitschke’s research has shown how different victim reactions (eg, pain versus negative emotions) can influence revenge-seeking behaviour, how revenge-seekers can experience satisfaction and pleasure from seeing their victim suffer, but also that revenge reactions can be bittersweet. While there are some limitations to their research, in that their findings can only be applied to provoked revengetaking and not other forms of aggression (eg, sexual aggression), and that acts of revenge may be different in real life than in a lab setting, their research is still critical in understanding revenge-taking behaviour.

Bio: Andreas Eder is Professor of Psychology at the JMU Würzburg in Germany. His main research interests lie in the motivational and emotional controls of human behaviour. Vanessa Mitschke is a Research Scientist at the Department of General Psychology II at the JMU Würzburg. Her main research interests lie in human aggression and punishment, and the psychophysiological measurement of its emotional consequences.

Funding: German Research Foundation; Collaborators: Dr. Anand Krishna (JMU Würzburg) and Professor Mario Gollwitzer (LMU Munich).

Contact for scientific information:

Andreas Eder, Röntgenring 10, 97070 Würzburg, Bavaria, Germany
Vanessa Mitschke, Röntgenring 10 , 97070 Würzburg

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