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CMB Monday Seminar - Carly Leonard

May 24, 2010
from 04:00 PM to 05:30 PM

267 Cousteau Place, Large Conference Room

Overt and covert capture of attention by magnocellular and parvocellular singletons

The generation of rapid saccades has been tied to magnocellular processing, due to direct M-pathway inputs to the superior colliculus as well as the predominance of magnocellular information in the dorsal stream. However, attention can also be guided by information encoded in the slower, but detail-rich, parvocellular processing stream. Although it is clear that input from both pathways can influence behavior, less is known about how salient task-irrelevant stimuli encoded by these two systems may influence covert and overt attentional processing. We used manual RT and oculomotor activity to reveal differences in interference caused by a singleton that predominantly activates the magnocellular system and one that isolates the parvocellular system. Participants performed the irrelevant singleton task (Theeuwes, 1991), searching for a unique shape while attempting to ignore an irrelevant but highly salient singleton distractor.  For a third of the trials, the singleton distractor was an isoluminant object of a different color (parvo-singleton); for another third, the singleton distractor differed in luminance from the other objects (magno-singleton); for the remaining third, no singleton distractor was present. We matched the salience of the two singleton distractor types such that there was an equivalent attentional capture effect on manual RT. Despite the equivalent manual RT effects, the magno-singleton distractor was more likely to attract an eye movement than the parvo-singleton distractor. When the first eye movement did go directly to the target, its latency was slowed in the presence of both magno- and parvo- singletons, indicating covert attentional competition. These results provide a more precise understanding of how underlying competitive attentional processes and intermediary saccadic behavior result in the explicit distraction effect found in manual RT.  

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