Information processing for unattended stimulus.

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In order to maintain a coherent behavior, we need to select some stimuli and ignore the others. However, sometimes the stimulus that should be ignored seems to influence the processing of the stimulus selected The aim of this study is to examine the nature of selective attention by focusing on the processing of unattended stimulus.In the first year, we used Stroop-like task to examine visual selective attention. In Stroop-like task, participants were asked to name the ink of the central color patch (target) while ignoring the color word (distracor) presented at the peripheral visual field. Reaction time for naming the ink of target would be faster when target is congruent with peripheral word than when target is incongruent with peripheral word. This effect is called Stroop-like effect and is supposed to be a good indicator of semantic processing of unattended stimulus. In this study, we manipulated processing demand to find the conditions under which Stroop-like effect disappeared. Ou … More r experiments showed that Stroop-like effect disappeared only when multiple stimuli similar to target were presented around the target. Other manipulations such as go/no go task did not extinguish the effect and sometimes produced a reversal Stroop-like effect. These results suggested that visual selective attention had a limitation in number of stimuli to process simultaneously. When the processing demand of task is low, distractor stimuli are processed to semantic level, resulting in interference. When the demand of task is high enough, distracor stimulus is not processed because of lack of available processing resources.In the second year, we examined the effect of a video image of a person speaking words on selective listening task. In selective listening task, target and distractor words are presented form two loudspeakers, and participants are asked to report the target words while ignoring the distractor words. In this study, we presented the video image of a person speaking a target words or distractor words as well as the target and distractor words form different loudspeakers. Selective listening of target words was improved when the video speaking target words was displayed, as compared with when the video of the person's mouth masked was displayed. When the video speaking distractor words was displayed, selective listening of the first target word was improved, but the performance of the other target words was deteriorated, as compared with when the video image with the masked mouth was displayed. These results showed that the visual image of a person speaking target words helped to distinguish target and distractor words and to follow the target list. The visual image of a person speaking distractor words helped to distinguish target and distractor words at first, but did not help to follow the target list. Probably visual attention to the movement of person's mouth congruent with distractor words induced to sound relocation due to ventriloquism.In addition to these studies, we attempted to examine the processing of unattended stimulus in other paradigms such as binocular rivalry, enumeration of affectively valenced words. Less