Abstract
PURPOSE: To dissociate the “where,” “what,” and “how” functions of the visual pathways by showing differential performance among task types. METHODS: Stimuli designed to differentially activate the parvocellular and magnocellular pathways, luminance-defined and equiluminant color-defined targets, were adjusted to be equisalient on an allocentric “where” location identification task. Participants responded to the same stimuli in two other visual tasks, a “how” aimed movement task and a “what” shape identification task. RESULTS: The same stimuli produced differential performance on the “what” and “how” tasks: specifically there was an advantage in both for the luminance-defined targets. CONCLUSION: This task-related contrast in visual sensitivity indicates differential recruitment of resources among task types. The results can be interpreted in terms of the “what,” “where,” and “how” functional dissociations of the ventral and dorsal streams Ungeleider & Mishkin, 1982; Milner & Goodale, 1995; Creem & Proffitt, 2001, and in terms of differences in sensitivity to low vs. high spatial frequencies of the processes carrying out these tasks.