Abstract
PURPOSE: Resent studies in visual attention have reported that attention is guided by the probabilistic information including the experimental tasks. In addition, some of these studies have suggested that the probability of the target appearance is available as an attentional cue without explicit knowledge regarding the probabilistic information. It is, however, unclear what kind of information participants can exploit as an attentional cue. In the present study, we investigated whether the probabilistic information implicitly defined by spatial location or symbolic cue was available for participants. METHODS: Participants were conducted the visual search task. They were instructed to discriminate the target orientation presented in the left or right placeholder as quickly and accurately as possible. In the experiment 1, the spatial probability of the target appearance was manipulated. In 60% of trials, target stimuli were presented in one placeholder (high probability condition), in 20% of trials, they were in another placeholder (low probability condition), and in the rest of 20% trials, no target stimuli were presented. In the experiment 2, cue validity was manipulated. The cues were colors of the center fixation. In 60% of trials, the color cues were valid (valid condition), in 20% of trials, the cues were invalid (invalid condition), and in the rest of 20% trials, no target stimuli were presented. RESULTS & CONCLUSION: In the experiment 1, the target discrimination in the high probability condition was faster than the low probability condition. On the other hand, in the experiment 2, there is no difference in the reaction times between valid and invalid condition. These results suggest when probabilistic information is defined by spatial locations, it leads attentional guidance despite that participants do not notice the information. In contrast, when probabilistic information is defined by symbolic cues, it does not lead attentional guidance.