ATTENTIONAL SETS DO NOT IMPAIR THE EFFECT OF DILUTION IN SELECTIVE ATTENTION
Perceptual load theory (Lavie & Tsal, 1994; Lavie, 1995) proposes that distractors interference can be avoided only in situations of high perceptual load. The theory has been supported by blocked design manipulations separating low load (when the target appears alone) and high load (when the target is embedded among neutral letters). Tsal and Benoni (2010a; Benoni & Tsal, 2010) recently showed that these manipulations confound perceptual load with "dilution" (the mere presence of additional items in high load situations). Theeuwes, Kramer, and Belopolsky (2004), independently questioned load theory by showing similar distractor interference under high load and low load when the two conditions are intermixed. Their results also challenge the dilution account, which offers a stimulus driven mechanism. In the present study we separated the effects of dilution and load and tested the influence of attentional sets (fixed vs. mixed) on each factor. We found that whereas the load effect is influenced by expectancy of trial type, the effect of dilution is not influenced by attentional sets.