Abstract
The parvocellular and magnocellular pathways are thought to be largely independent visual processing streams, which process different aspects of visual information. The magnocellular pathway is thought to process information about the location and movement of objects, while the parvocellular pathway is thought to process information that is useful for recognition and identification of objects. This study used a dual task methodology to test the hypothesis that the two pathways draw from independent pools of attentional resources. We predicted that engaging in two search tasks that were processed by different pathways would result in less dual task performance decrement than two tasks that were processed by the same pathway. Two groups of eight small disks were simultaneously presented for 200 milliseconds. Each group contained a single target. Observers were asked to identify the location of the target in each group. Magnocellular targets were defined by brief luminance transients and parvocellular targets were defined by color. Targets that yielded approximately 75% correct in single task conditions were used in the dual task condition. Results showed little or no dual task interference when two transient targets or a color target and a transient target were paired. A small dual task performance decrement was observed when the two groups of stimuli contained identical target and distractor colors. A larger decrement was observed when the targets in the two groups differed in color. An even larger decrement was observed when the roles of target and distractor colors were reversed in the two tasks. Two search tasks that were mediated by different pathways or by the magnocellular pathway showed little dual task performance decrement. However two search tasks that were mediated by the parvocellular pathway resulted in varying degrees of dual task interference, depending on the target and the distractor colors in the two tasks.