Knowledge of objects’ physical properties implicitly guides attention during visual search.

Our interactions with the world are guided by our understanding of objects’ physical properties. When packing groceries, we place fragile items on top of more durable ones and position sharp corners so they will not puncture the bags. However, physical properties are not always readily observable, and we often must rely on our knowledge of attributes such as weight, hardness, and slipperiness to guide our actions on familiar objects. Here, we asked whether our knowledge of physical properties not only shapes our actions but also guides our attention to the visual world. In a series of four visual search experiments, participants viewed arrays of everyday objects and were tasked with locating a specified object. The target was sometimes differentiated from the distractors based on its hardness, while a host of other visual and semantic attributes were controlled. We found that observers implicitly used the hardness distinction to locate the target more quickly, even though none reported being aware that hardness was relevant. This benefit arose from fixating fewer distractors overall and spending less time interrogating each distractor when the target was distinguished by hardness. Progressively more stringent stimulus controls showed that surface properties and curvature cues to hardness were not necessary for the benefit. Our findings show that observers implicitly recruit their knowledge of objects’ physical properties to guide how they attend to and engage with visual scenes.