The neural correlates of justified and unjustified killing: an fMRI study

Abstract

Despite moral prohibitions on hurting other humans, some social contexts allow for harmful actions such as killing of others. One example is warfare, where killing enemy soldiers is seen as morally justified. Yet, the neural underpinnings distinguishing between justified and unjustified killing are largely unknown. To improve understanding of the neural processes involved in justified and unjustified killing, participants had to imagine being the perpetrator whilst watching 'first-person perspective' animated videos where they shot enemy soldiers ('justified violence') and innocent civilians ('unjustified violence'). When participants imagined themselves shooting civilians compared with soldiers, greater activation was found in the lateral orbitofrontal cortex (OFC). Regression analysis revealed that the more guilt participants felt about shooting civilians, the greater the response in the lateral OFC. Effective connectivity analyses further revealed an increased coupling between lateral OFC and the temporoparietal junction (TPJ) when shooting civilians. The results show that the neural mechanisms typically implicated with harming others, such as the OFC, become less active when the violence against a particular group is seen as justified. This study therefore provides unique insight into how normal individuals can become aggressors in specific situations.

Keywords: conflict; intentional harm; morality; orbitofrontal cortex; violence.

Fig. 1

Schematic representation of an example block from the ‘Soldiers’ condition. Each block included three video clips of 6 s from the same condition and ended with a 5 s response window.

Fig. 2

Significant brain activation differences in the Civilians minus Soldiers contrast (A) and Soldiers minus Civilians contrast (B) displayed on the ch2better template using MRIcron (http://www.mricro.com/mricron). See also Supplementary Table S1 for the main effect of conditions analysis, Civilians minus Control contrast and Soldiers minus Control contrast.

Fig. 3

The more guilt participants felt about shooting the civilians vs soldiers, the higher the % signal change in left and right OFC. The same regression in SPM is displayed on the ch2better template using MRIcron (http://www.mricro.com/mricron).

Fig. 4

Psychophysiological analysis. Significant increased connectivity between left OFC and left and right TPJ for the Civilians minus Soldiers contrast displayed on a ch2better rendered template using MRIcron (http://www.mricro.com/mricron).