Effects of type of design (blocked vs. randomized) on Stroop and emotionalStroop tasks

The purpose of the present study was to investigate the effects of stimulus fragmentation on Stroop and emotional Stroop interference and facilitation effects when stimuli at all fragmentation levels were blocked by condition as well as when they were totally randomized across conditions. Under bloc ked conditions, in which stimuli from the same condition (e.g., congruent, incongruent, control conditions) at all levels of fragmentation were presen ted in the same block, interference appeared even at the most fragmented le vel, and increased linearly until level 8. The same occurred with facilitat ion. Randomized designs, on the other hand, showed that interference did no appear until level 4 and increased linearly until level 8, whereas facilit ation disappeared. Previous work from our laboratory showed that words are objectively identified at level 4. The findings suggest the existence of (a )over dot response set in blocked designs, which in turn may speak against the automaticity of the Stroop effect.