What I Don’t Know Can Hurt You: Collateral Combat Damage Seems More Acceptable when Bystander Victims are Unidentified

Four experiments (N=1563 American mTurkers) utilized a realistic moral dilemma: a military pilot must decide whether to bomb a dangerous enemy target, also killing a bystander. Few people endorsed bombing when the bystander was an innocent civilian; however, when the bystander’s identity was unknown, more than twice as many people endorsed the bombing. Follow-up studies tested why: people tend to assume an unidentified bystander is an enemy. Humanizing the bystander with a photograph and family history reduced bombing, an effect mediated via reduced inferences of enemy group membership—even though humanizing information contained no allegiance information. This pattern appears to reflect a general bias, rather than motivated reasoning about a specific conflict, as people responded similarly to fictional targets. This work has implications for conflicts where bystanders of uncertain allegiance or identity are common by revealing a potentially deadly bias: people often assume unidentified bystanders are guilty unless proven innocent.