Omission and commission in judgment and choice

Subjects read scenarios concerning pairs of options. One option was an omission, the other, a commission. Intentions, motives, and consequences were held constant. Subjects either judged the morality of actors by their choices or rated the goodness of decision options. Subjects often rated harmful omissions as less immoral, or less bad as decisions, than harmful commissions. Such ratings were associated with judgments that omissions do not cause outcomes. The effect of commission is not simply an exaggerated response to commissions: a reverse effect for good outcomes was not found, and a few subjects were even willing to accept greater harm in order to avoid action. The “omission bias” revealed in these experiments can be described as an overgeneralization of a useful heuristic to cases in which it is not justified. Additional experiments indicated that subjects' judgments about the immorality of omissions and commissions are dependent on several factors that ordinarily distinguish omissions and commissions: physical movement in commissions, the presence of salient alternative causes in omissions, and the fact that the consequences of omissions would occur if the actor were absent or ignorant of the effects of not acting.