Effects of luminance change in preview search: Offsets and onsets can be concurrently prioritized but not in isolation

Two experiments are performed to investigate how luminance change contributes to prioritized selection of new over old elements. Experiment 1 demonstrates that observers prioritize items that undergo a luminance change irrespective of the direction of that change. Experiment 2 shows that foreknowledge concerning the direction of luminance change signaling the target does not allow observers to prioritize the selection of luminance onsets over offsets and vice versa. The results suggest that prioritized selection of new over old elements is mediated by a general mechanism that is sensitive to luminance change, irrespective of its direction.