Attentional focus, processing load, and Stroop interference
Although the effects of attentional focus and perceptual load on selective attention are well-known when targets and distractors are distinct objects that occupy separate locations, there has been little examination of their role when relevant and irrelevant information pertains to the same object. In four experiments, participants were shown Stroop color words or strings of letters, and the task was speeded color identification. When participants’ attentional focus was manipulated via cue validity or precue size, greater Stroop interference was observed when the attentional focus was narrow compared to when it was broad. However, when participants were induced to adopt a comparable attentional focus in a dual-task paradigm, the differential Stroop interference was eliminated. Furthermore, contrary to the prediction of the perceptual load hypothesis, different levels of processing load did not lead to differential Stroop interference. These results emphasize the importance of stimulus structure in understanding distractor processing. They indicate that when relevant and irrelevant information belong to the same object, narrowing attentional focus increases distractor processing, and perceptual load has a negligible effect on the extent of distractor processing.