Capture of Attention to Threatening Stimuli without Perceptual Awareness

Visual images that convey threatening information can automatically capture attention [1-4]. One example is an object looming in the direction of the observer-presumably because such a stimulus signals an impending collision [5]. A critical question for understanding the relationship between attention and conscious awareness is whether awareness is required for this type of prioritized attentional selection [6]. Although it has been suggested that visual spatial attention can only be affected by consciously perceived events [7], we show that automatic allocation of attention can occur even without conscious awareness of impending threat. We used a visual search task to show that a looming stimulus on a collision path with an observer captures attention but a looming stimulus on a near-miss path does not. Critically, observers were unaware of any difference between collision and near-miss stimuli even when explicitly asked to discriminate between them in separate experiments. These results counter traditional salience-based models of attentional capture, demonstrating that in the absence of perceptual awareness, the visual system can extract behaviorally relevant details from a visual scene and automatically categorize threatening versus nonthreatening images at a level of precision beyond our conscious perceptual capabilities.