Theeuwes (1991, 1992) found that a salient but task-irrelevant color singleton would increase the response time to the target form singleton, and he proposed that this was because the salient distractor captured attention before it was shifted to the target, which is known as the automatic capture hypothesis. He further suggested the relative saliency of the color singleton would determine whether it could capture attention, but so far there hasn’t been any experiments revealing specifically how different distractor saliency conditions on a continuous spectrum would have an effect on attentional capture. In this research, we examined this question within multiple attention-guiding dimensions, including color, size and orientation (Wolfe & Horowitz, 2004).