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The Social Nature of Killing-induced Guilt

August 17, 2013

By David Webber (University of Alberta), Jeff Schimel (University of Alberta), Andy Martens (University of Canterbury in New Zealand), Joseph Hayes (York University) and Erik Faucher (University of Alberta)

Just more than 10 years ago, the world engaged in a coordinated effort, estimated at more than 10 million strong, against the Iraq War. In countless cities across the globe, people stood up to have their voices heard against the invasion of Iraq. Although the reasons against war are numerous, protestors usually express disdain for the war effort itself, while remaining supportive of the actual soldiers entrenched in battle. Many times, it is the very livelihood of these soldiers that motivates the public to speak out in the first place.

A question that arises from situations like this, however, is whether soldiers turn to the greater public to help them determine if their actions at war are acceptable. Just like an audience member watching a romantic comedy may look to the reactions—specifically laughter—of other members in the theater to determine if the film is funny, we thought a soldier may look to the public to determine if their fighting is moral. In this sense, speaking out against or refusing to go to war are clear indications that the killing taking place is unacceptable and immoral. And if the invalidation of the public informs on the immorality of one’s actions, this should increase the level of distress and guilt experienced as a result. These are the ideas that inspired a series of studies recently published in the Personality and Social Psychology Bulletin (Webber, Schimel, Martens, Hayes, & Faucher, 2013).

Our research started with the understanding that killing an enemy combatant is one of the best predictors of whether a soldier experiences trauma after their time in battle (i.e., Maguen et al., 2011), and that guilt is a cornerstone emotion in this type of trauma (Litz et al., 2009). We then sought to examine if we could change the levels of guilt that people feel after killing by manipulating the actions of the “general public.” In a series of studies we replicated the “war” setting within our laboratory. Instead of using soldiers required to kill enemy combatants in service of their country, we used college students required to kill insects in the service of advancing science. And instead of using protestors decrying the acts of war, we crafted situations where their college peers either validated or invalidated the act of killing insects.


Figure 1. The bug “grinder.”

In two studies, participants assumed the role of exterminator and completed an insect extermination task (adapted from Martens, Kosloff, Greenberg, Landau, & Schmader, 2007). Participants deposited ten insects into a modified coffee grinder. Upon depressing the “activation button” the blades of the grinder engaged and they heard what they believed to be the sound of insects being decimated. In actuality, the grinder was modified such that no insects were harmed, and participants only heard the “killing” of bits of Styrofoam (see Figure 1).

After killing, perceptions of validation and invalidation were experimentally manipulated. In our first study this was accomplished by using an actor pretending to be another participant in the study. This actor either willingly agreed to participate in the killing task, thus validating the act of killing, or refused to participate and abruptly exited the lab, thus invalidating the kill. In our second study, participants were led to believe that a group of 34 previous participants either willingly killed or refused to kill. Immediately afterwards, behavioral and self-report indices of guilt and distress were assessed.

Across both studies we found higher levels of guilt when the act of killing had been invalidated by their peers. When participants perceived that their peers had also killed, and were thus approving of killing insects, they were protected from feelings of guilt. When, on the other hand, they perceived that their peers disapproved of killing, they came to view their actions as immoral, as indicated through increased levels of guilt and distress.

We also included control conditions in both studies where participants were not provided with any social information about their peers. We found that even when not provided with validating information, participants assumed their peers would do the same as them. Importantly, this assumption of validation was also effective at keeping guilt levels low. Thus, whenever participants viewed killing as valid, whether the result of an assumption or social evidence, the act of killing was experienced as less distressing and guilt-inducing.

We believe these results speak to the social nature of morality. Because this research was inspired by the circumstances of veterans returning from war, we focused on the morality of killing, and the ramifications of social influence on one’s ability to justify those actions as moral. These results demonstrate that feelings like guilt, that we commonly perceive to be very individual and personal, are indeed influenced by the social context. They also provide a glimpse into one variable that can aid us in determining why killing can be so traumatic and distressing under certain situations and for certain individuals, but not all.

Author Information

david_webber David Webber is a PhD candidate at the University of Alberta. His research examines the role of social psychological variables in killing decisions, and psychological processes that occur when one experiences a threat to valued meaning structures.

jeff_schimelJeff Schimel is an Associate Professor at the University of Alberta. His research examines the psychological functions of cultural worldviews and self-esteem.

andy_martensAndy Martens is an Assistant Professor at the University of Canterbury in New Zealand. He examines the escalation of violence, connections between physiology and psychological health, and the influence of existential concerns.

joseph_hayesJoseph Hayes is a postdoctoral researcher at York University. His research examines the psychological functions of beliefs, values, and goals. He is interested in how people respond when these structures are threatened, as well as the personal and social consequences of such responses.

erik_faucherErik Faucher is a PhD candidate at the University of Alberta. His research interests pertain to the relationship between self-control and self-esteem. His research interests pertain to the relationship between self-control and self-esteem.


Litz, B. T., Stein, N., Delaney, E., Lebowitz, L., Nash, W. P, et al. (2009). Moral injury and moral repair in war veterans: A preliminary model and intervention strategy. Clinical Psychology Review, 29, 695-706. doi:10.1016/j.cpr.2009.07.003

Maguen, S., Vogt, D. S., King, L. A., King, D. W., Litz, B. T., & Knight, S. J. et al. (2011). The impact of killing on mental health symptoms in Gulf War veterans. Psychological Trauma: Theory, Research, Practice, and Policy, 3, 21-26. doi: 10.1037/a0019897

Martens, A., Kosloff, S., Greenberg, J., Landau, M. J., & Schmader, T. (2007). Killing begets killing: Evidence from a bug-killing paradigm that initial killing fuels subsequent killing. Personality and Social Psychology Bulletin, 33, 1251-1264.doi: 10.1177/0146167207303020

Webber, D., Schimel, J., Martens, A., Hayes, J., & Faucher, E. H. (2013). Using a bug-killing paradigm to understand how social validation and invalidation affect the distress of killing. Personality and Social Psychology Bulletin, 36, 470-481.

Photo Credit: Photograph of a protest against the war in Iraq, taken from Hungerford Bridge, in Embankment London. 15th Febuary 2003., Image courtesy of Simon Rutherford. This file is licensed under the Creative Commons Attribution 2.0 Generic license. under the terms of the cc-by-2.0. This image was originally posted to Flickr by Simon Rutherford at

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