When the killing has been done: Exploring associations of personality with third-party judgment and punishment of homicides in moral dilemma scenarios

Killing people is universally considered reprehensible and evokes in observers a need to punish perpetrators. Here, we explored how observers' personality is associated with their cognitive, emotional, and punishing reactions towards perpetrators using data from 1,004 participants who responded to a set of fifteen third-party perspective moral dilemmas. Among those, four scenarios (architect,life boat,footbridge,smother for dollars) describing deliberate killings were compared to investigate the role of the content features "motive for killing" (selfish vs. utilitarian) and "evitability of victims' death". Participants' moral appropriateness ratings, emotions towards perpetrators, and assigned punishments revealed complex scenario-personality interactions. Trait psychopathy was associated with harsher punishments in all scenarios but also with less concern about killing in general, an increased moral appreciation of utilitarian motives for killing, and a reduced concern about the killing of avoidable victims. Need for cognition was associated with considering a utilitarian motive for killing as a mitigating factor, while intuitive/authority-obedient thinking was linked to a strong focus on avoidability of harm as an aggravating factor when assigning punishments. Other-oriented empathy, trait anxiety, and justice sensitivity did not account for differences in third-party punishments. Our explorative findings highlight the importance of inter-individual differences for moral decision making and sense of justice.