Abstract
Recognition memory is generally accompanied by awareness, such as when a person recollects details about a prior event or feels that a previously encountered face is familiar. Moreover, recognition is usually benefited by attention. I will describe a set of experiments that yielded unprecedented dissociations between recognition, attention, and awareness. These effects were produced by carefully selecting experimental parameters to minimize contributions from memory encoding and retrieval processes that normally produce awareness, such as semantic elaboration. Fractal images were viewed repeatedly, and repeat images could be discriminated from novel images that were perceptually similar. Discrimination responses were highly accurate even when subjects reported no awareness of having seen the images previously, a phenomenon we describe as implicit recognition. Importantly, implicit recognition was dissociated from recognition accompanied by awareness based on differences in the relationship between confidence and accuracy for each memory type. Diversions of attention at encoding greatly increased the prevalence of implicit recognition. Electrophysiological responses obtained during memory testing showed that implicit recognition was based on similar neural processes as implicit priming. Both implicit recognition and implicit priming for fractal images included repetition-induced reductions in the magnitude of neural activity in visual cortex, an indication of visual processing fluency. These findings collectively indicate that attention during encoding biases the involvement of different memory systems. High attention recruits medial temporal structures that promote memory with awareness whereas low attention yields cortical memory representations that are independent from medial temporal contributions, such that implicit recognition can result.