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Geniva Liu, James T. Enns; Visual identification slows planning, but not execution, of concurrent visually guided action. Journal of Vision 2004;4(8):444. doi: https://doi.org/10.1167/4.8.444.
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The dual systems theory (Milner & Goodale, 1995) outlines two systems for human visual processing: a ventral stream for conscious perception of objects and a dorsal stream for guiding actions. This theory raises the possibility of separate mechanisms of attention, which leads to the prediction that there will be minimal interference when performing two tasks that each rely on separate streams. The present study examined dual-task performance in concurrent “ventral” and “dorsalrd tasks. Participants identified a letter target within a centrally-presented rapid sequence of digits (ventral task) while at the same time pointing quickly and accurately to a peripheral target that appeared suddenly in one of several locations (dorsal task). The temporal interval was varied such that the pointing target either preceded or followed the letter target. In a single-task control condition, participants ignored the central stream of digits and only pointed to the peripheral target. Results indicated that: (1) pointing initiation times were longest when the pointing target preceded the letter target and decreased monotonically as the pointing target presentation was delayed relative to the letter target, and (2) pointing movement time and accuracy was unaffected by concurrent letter identification. We interpret this as evidence for dual task interference in the planning, but not in the execution of visually guided action.
Natural Sciences and Engineering Research Council of Canada, Michael Smith Foundation for Health Research
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