Pattern span: a tool for unwelding visuo-spatial memory.

Evidence showing that non-verbal short-term memory has distinct visual and spatial/sequential components is reviewed. A new test, The Visual Patterns Test (VPT), which was designed to measure short-term visual memory largely shorn of its spatio-sequential component, is described. Correlational studies of the VPT and the Corsi Blocks Test with healthy subjects and brain-damaged patients indicate a separation between visual and sequential abilities. This separation of function is supported by double dissociations shown by patients. Moreover, in a selective interference experiment, the VPT and the Corsi tests were found to show a double dissociation pattern of interference from visual and spatio sequential subsidiary tasks, respectively. The present results are discussed in relation to other findings in the literature, and it is concluded that non-verbal short-term memory can indeed be viewed as comprising distinct visual and spatio-sequential components. The VPT will be a useful neuropsychological instrument for measuring the visual component.