Abstract
Stimuli attract attention when they appear suddenly, when they differ from other stimuli, or when they otherwise become salient. Can absent stimuli attract attention too? The missing tooth in a child’s smile, or the missing wheel of a bicycle, often seem salient and noticeable. Previously, we obtained initial evidence that visual processing privileges absent objects. Here, we dramatically expand on this work by exploring the timecourse and mechanism of absence-enhanced visual processing. In Experiment 1, subjects saw line-drawings of objects missing a part (e.g., a butterfly missing a wing). After onset (150ms), a probe appeared on the object or in empty space, and subjects classified it accordingly. Crucially, empty-space probes appeared on an “absent” part (i.e., empty space where missing parts “should” have been) or on true empty space. Even at such short probe-onset asynchronies, subjects classified “absent” probes faster than true empty probes, suggesting attentional prioritization of absent parts. In Experiment 2, stimuli appeared inside a bounding box in two conditions: (1) with enough space for the missing part to have fit had it been there (Room); and (2) with stimuli slightly skewed such that the missing part could not have fit (No Room). Subjects classified “absent” probes slower than object probes in No-Room compared to Room—as if the bounding box interfered with absence-guided attentional enhancement. In Experiment 3, stimulus and probe appeared simultaneously, massively reducing the previously observed interference; this ruled out that the interference was produced by the crowded position of the stimuli near the edge of the box. Together, these results suggest that absence-enhanced attention is fast and automatic—unlikely to be driven by voluntary mental imagery—and an active process that can be disrupted via spatial interference. Not only can present objects attract attention, but absences are salient too.