In a strict legal sense, motive is often irrelevant in U.S. criminal law. Whether one smothered their grandmother with a pillow to ease her pain or to fraudulently collect her social security benefits, they are legally guilty of murder all the same. Yet anyone who has watched a courtroom drama or sat in the jury box knows the prominent role that establishing motive seems to play in influencing legal decision-makers. Why is motive so pivotal, so psychologically powerful for most people? We briefly review the existing literature on the psychology of motive, then introduce an adaptationist framework as a new lens for examining this question. In particular, we consider how motive assists perceivers in inferring actors’ welfare trade-off ratios, with important implications for legal judgments and willingness to punish.
Williams et al. (Fri,) studied this question.