Among all visual cortical areas, the primary visual cortex (V1) has the most monocular cells and is least associated with visual awareness. The eye of origin information is mainly available only in V1 since cortical neurons beyond V1 are mostly binocular. It has also been known that human observers are typically unable or inconfident to identify eye of origin of visual input. I will show psychophysical findings that unique eye of origin can attract attention automatically, just like a unique color, e.g., a red item among green ones, can. This is the case even when the observers were unable to detect the unique eye of origin by forced choice, i.e., when they do not even have the blind sight. Regardless of whether the observers were aware of or informed about the unique eye of origin, a unique eye of origin can exogenously cue attention to a task relevant location to improve visual performance, can decrease reaction time to find a target when it is at the target location in a visual search task, or increase the reaction time when it is away from the target location. The data also suggest that the unique eye of origin is salient enough to successfully compete for visual attention with orientation singleton which is considered salient enough for pop out. These findings support the theoretical proposal that the primary visual cortex creates a bottom-up saliency map (Li 1999 2002), and suggest that strong bottom-up attentional attraction can be dissociated from visual awareness.

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