A Systematic Perspective on Human Memory

John Gabrieli

Stanford University

Delineation of the functional architecture of human memory has been a major goal for psychology and for cognitive neuroscience. Beginning with the seminal studies of Ebbinghaus, one approach towards this delineation has been purely behavioral and not included any consideration of the actual neural architecture of human memory. This behavioral approach has been highly productive, but limited largely to the memorization of word lists. Further, theoretical progress has stagnated for the past decade as researchers debate whether one-process or two-process (e.g., recollection and fluency) models better account for verbal recognition memory. A second, memory systems, approach has attempted to identify specific neural networks that mediate specific mnemonic processes. This approach has several strengths, but also some limitations. First, only the systems approach can account for the many dissociations seen in patients with brain injuries that were unanticipated by behavioral theory, such as dissociations between explicit and implicit memory performance, between multiple kinds of explicit memory performance, and between multiple kinds of implicit memory performance. Second, the memory systems approach has broadened theorizing about memory to include many kinds of learning, ranging from repetition priming to classical conditioning to cognitive skill learning, in a synthetic framework. Third, the memory systems approach provides for the greatest number of constraints upon theory because it is informed both by behavioral and by neuroscience data. In turn, these constraints may provide a level of specificity and generalization that is accurate for principles that govern particular forms of memory. Fourth, the memory systems approach has been generative, from the discovery of implicit forms of memory to integration with novel functional imaging techniques. One critique of the systems approach is that there may be many memory systems, but it is unclear why that is a weakness of this approach if there are actually many memory systems in the human brain. One important limitation of the memory systems approach is that it does not characterize the actual processes mediated by the systems (i.e., that a form of memory depends upon a particular brain structure does not explain what mnemonic process is mediated by that structure). That, however, is a limitation of theory and knowledge in both psychology and neuroscience.