Source monitoring and multivariate signal detection theory, with a model for selection

Participants in source monitoring studies, in addition to determining whether an item is old or new, also discriminate the source of the item, such as whether the item was presented in a male or female voice. This article shows how to apply multivariate signal detection theory (SDT) to source monitoring. An interesting aspect of one version of the source monitoring procedure, from the perspective of multivariate SDT, is that it involves a type of selection, in that a discrimination response is observed only if the detection decision is that an item is old. If the selection is ignored, then the estimate of the discrimination parameter can be biased; the nature and magnitude of the bias are illustrated. A bivariate signal detection model that recognizes selection is presented and its application is illustrated. The approach to source monitoring via multivariate SDT provides new results that are informative about underlying psychological processes.