A trial began with subjects fixating the center of the screen. When subjects pressed a button, an image appeared with 9 placeholders (gray X's). |
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After 1 sec., a cue (the target to find) appeared to either the right or the left of the placeholder image. Subjects were instructed to look at the cue. |
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600 msec after the saccade was detected, 3 late onset X's appeared (these were brighter than the placeholder X's in order to make them more visible in the periphery. (In half of the trials, 4 X's appeared). |
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100 msec later, the 3 late onset X's disappeared. |
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48 msec later, the 3 late onset X's reappeared. This was a signal to subjects to send their eyes back into the main image in order to search for the target in one of the 3 late onset locations. |
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During the saccade, all the X's changed to either red or green titled lines. Note that a search among the objects in the 3 late onset locations constitutes a conjunction search. If subjects searched the entire display, it would be a conjunction search among 12, rather than 4, objects. |
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