| Summary: | 碩士 === 國立中正大學 === 心理學研究所 === 99 === Perceptual load theory suggested that, when a task carries a high perceptual load, distractor processing is decreased compared with a task that have low perceptual load. Torralbo and Beck (2008) varied the density of letters and the results suggested that neural competition among letters may be the reason or mechanism for which perceptual loading occurs. In addition, it is known that attentional focus can be modulated by the arrangement of stimuli. However, the manner in which the size of attentional focus affects perceptual load is less clear. Thus, the purpose of this thesis was to examine whether (a) stimulus density can define perceptual load when the stimuli are in color and (b) attentional focus can modulate distractor processing. In the experiment 1A, we replicated the study of Torralbo and Beck (2008) and then changed the letters into color blocks in experiment 1B. Neither experiment could be fully replicated. In experiment 2, reducing the distance between stimuli and the distance of the stimuli to the fixation point showed that the distractor effects were larger in the low-density versus the high-density condition, which is consistent with the perceptual load theory. In experiment 3, another density condition (a much wider distance between stimuli) was added to manipulate the size of attentional focus. In experiment 3A, the lowest density condition represented 10% of total trials, but in experiment 3B, it represented 50% of trials. The remaining trials were equally distributed between the two other density conditions. The results showed that experiment 3A, but not experiment 3B, had the largest distractor effects in the lowest density condition. In conclusion, processing blocks of color is different from letter processing, and the perceptual load theory for color processing could be enhanced in the central foveal area. Finally, attentional focus can be modulated by the distribution of trials across conditions and then further modulated central distractor processing.
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