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Refining the Taxonomy of Memory

Humans can remember things by means of several types of memory. Two of the most important are declarative memory (conscious recollection of facts and events) and skill memory (gradual acquisition of motor abilities, but without conscious awareness). In a report in this issue, Knowlton et al. (p. 1399) show that patients with Parkinson's disease (and therefore with impaired dopamine input to the striatum) are impaired in skill memory, as measured by a newly designed discrimination learning task, but that their declarative memory is intact. Robbins, in his Perspective, explains what these results mean for the taxonomy of human memory.