Attentional modulation of perception of spatial position does not necessitate visual awareness

In spatial localization, the “attentional repulsion effect” has been demonstrated that a briefly presented visual cue that draws attention leads to displacement of the perceived position of subsequent stimulus presented nearby to a direction opposite to the cue. The similar “attentional attraction effect” has also showed that localization is subject to retrospective influence of attention drawn by objects appearing afterwards. Here, we attempted the following question: does attentional modulation of spatial representation necessitate visual awareness to occur? In Experiment 1, we examined the attentional repulsion and attraction effects under near absence of visual awareness. Briefly presented positional cues were rendered invisible by immediate backward masking of stimuli that covered all possible cue locations. Observers judged the horizontal alignment of two vernier targets that were preceded or followed by the cue. In a separate session, we confirmed that observers could not reliably detect the location of the masked cue. The results revealed that the repulsion and attraction effects occurred even with the masked cues, though the effect magnitudes were smaller than those without the mask. In Experiment 2, we employed a dual-task paradigm that required observers to report the location of both the target and masked cue. The significant repulsion and attraction effects were associated with the actual cue locations, not with the reported cue locations. These results suggested that prospective and retrospective attentional modulation of spatial location does not require visual awareness to occur and the underlying process is based on unconscious attentional shift, rather than perception of the cues.