Dienes & Perner present a hierarchical model that addresses the nature – implicit versus explicit – of knowledge in areas as diverse as learning, memory, and visual perception. This framework appears difficult to apply to complex situations, such as those involving implicit learning, because of the indeterminacy that remains regarding knowledge at the low-level in the hierarchy. These reservations should not detract from the positive features of this model. Among its other advantages, it is well adapted to priming phenomena in which the information responsible for the individual's behavior can be precisely defined.