Radiologists could distinguish between the normal and abnormal radiographic features in a specific test set much better when searching chest radiographs for any abnormal findings than when explicitly evaluating each individual test feature without searching the films. Because the radiologists' ability to separate the subtle test abnormalities from normal variations was severely reduced by directing attention to these particular radiographic features, the recognition of abnormal findings may have been augmented by perceptual mechanisms that functioned only during the process of visual search. These could be visual mechanisms, developed through experience in scanning familiar examinations, that detect “unusual” pattern configurations and automatically draw the radiologist's attention to features that are likely to represent pathology.