Display sequence for the 3 Late Onset condition (Feature Search):

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).

 

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.

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 the trials, there were 4 X's).

100 msec later, the 3 late onset X's disappeared.

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.

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 feature search. However, if subjects searched the entire display, it would be a conjunction search.

 

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