Use of a Rasch model to predict response times to utilitarian moral dilemmas

Abstract

A two-systems model of moral judgment proposed by Joshua Greene holds that deontological moral judgments (those based on simple rules concerning action) are often primary and intuitive, and these intuitive judgments must be overridden by reflection in order to yield utilitarian (consequence-based) responses. For example, one dilemma asks whether it is right to push a man onto a track in order to stop a trolley that is heading for five others. Those who favor pushing, the utilitarian response, usually take longer to respond than those who oppose pushing. Greene’s model assumes an asymmetry between the processes leading to different responses. We consider an alternative model based on the assumption of symmetric conflict between two response tendencies. By this model, moral dilemmas differ in the “difficulty” of giving a utilitarian response and subjects differ in the “ability” (tendency) to give such responses. (We could just as easily define ability in terms of deontological responses, as the model treats the responses symmetrically.) We thus make an analogy between moral dilemmas and tests of cognitive ability, and we apply the Rasch model, developed for the latter, to estimate the ability-difficulty difference for each dilemma for each subject. We apply this approach to five data sets collected for other purposes by three of the co-authors. Response time (RT), including yes and no responses, is longest when difficulty and ability match, because the subject is indifferent between the two responses, which also have the same RT at this point. When we consider yes/no responses, RT is longest when the model predicts that the response is improbable. Subjects with low ability take longer on the “easier” dilemmas, and vice versa.