A dose of ruthlessness: interpersonal moral judgment is hardened by the anti-anxiety drug lorazepam

Neuroimaging data suggest that emotional brain systems are more strongly engaged by moral dilemmas in which innocent people are directly harmed than by dilemmas in which harm is remotely inflicted. In order to test the possibility that this emotional engagement involves anxiety, we investigated the effects of 1 mg and 2 mg of the anti-anxiety drug lorazepam on the response choices of 40 healthy volunteers (20 male) in moral-personal, moral-impersonal, and nonmoral dilemmas. We found that lorazepam caused a dose-dependent increase in participants' willingness to endorse responses that directly harm other humans in moral-personal dilemmas but did not significantly affect response choices in moral-impersonal dilemmas or nonmoral dilemmas. Within the set of moral-personal dilemmas that we administered, lorazepam increased the willingness to harm others in dilemmas where harm was inflicted for selfish reasons (dubbed low-conflict dilemmas) as well as responses to dilemmas where others were harmed for utilitarian reasons (i.e., for the greater good, dubbed high-conflict dilemmas). This suggests that anxiety exerts a general inhibitory effect on harmful acts toward other humans regardless of whether the motivation for those harmful acts is selfish or utilitarian. Lorazepam is also a sedative drug, but we found that lorazepam slowed decision times equally in all 3 dilemma types. This finding implies that its specific capacity to increase ruthlessness in moral-personal dilemmas was not a confound caused by sedation.