Does partial difficult search help difficult search?

Olds, Cowan, and Jolicoeur (2000a, 2000b) showed that exposure to a display that affords pop-out search a target among distractors of only one color) can assist processing of a related display that requires difficult search. They added distractors of an additional color to the initial simple display and analyzed response time distributions to show that exposure to the initial display aided subsequent search in the difficult portion (this finding was called search assistance). To test whether search assistance depends on perceptual grouping of the initial items, we presented initial items that were more difficult to group (two colors of distractors, instead of just one).