Retrospective triggering of conscious perception by an interstimulus interaction.

Attention facilitates conscious perception of a visual stimulus at an attended location. Interestingly, a recent study (using the Posner spatial-cueing task) reported that attention facilitated conscious perception even when it was cued after a stimulus was gone (postcued-attention or retroperception effect). Here, we show that this effect can be induced without any contribution of attention. Contrary to previous situations, we fixed a position of a target (Gabor patch) and cue (luminance change of a circle encompassing the target) across trials so that subjects always could allocate their full attention to the target position. The cue (luminance change) improved objective and subjective visibility of the nearby target even when it was given ∼200 ms after the target's offset. This retrospective improvement was diminished when a shape of the cue was changed from a circle to a dot pattern, suggesting that the improvement emerged from a visual interaction (combinations of shapes) between the circular cue and target. Those results indicated that a local visual interaction between the target and cue is sufficient to trigger consciousness of the target, revealing a new type of retroperception effect mediated by sensory (nonattentional) mechanisms.