Mary J Bravo | Search PubMed

PubMed2004

Recognizing and segmenting objects in clutter.

When viewing a cluttered scene, observers may not be able to segment whole objects prior to recognition. Instead, they may segment and recognize these objects in a piecemeal way. Here we test whether observers can use the appearance of one object part to predict the location and appearance of other object parts. During several training sessions, observers studied an object against a blank background. They then viewed this object against a background of clutter that camouflaged some parts of the object while leaving other parts salient. The observer's task was to find the camouflaged part. We varied the symmetry of the salient part with the expectation that as this symmetry decreased, the information about the camouflaged part's location and appearance would increase and this would facilitate search. Our results suggest that observers can use the salient part to predict the location, but not the appearance, of the camouflaged part.

Discrimination, Psychological↗

PubMed2004

Search for a category target in clutter.

An airport security worker searching a suitcase for a weapon is engaging in an especially difficult search task: the target is not well-specified, it is not salient, and it is not predicted by its context. Under these conditions, search may proceed item-by-item. In the experiment reported here we tested whether the items for this form of search are whole familiar objects. Our displays were composed of color photographs of ordinary objects, that were either uniform in color and texture (simple), or had two or more parts with different colors or textures (compound). The observer's task was to detect the presence of a target belonging to a broad category (food). We found that when the objects were presented in a sparse array, search times to find the target were similar for displays composed of simple and compound objects. But when the same objects were presented as dense clutter, search functions were steeper for displays composed of compound objects. We attribute this difference to the difficulty of segmenting compound objects in clutter: compared with simple objects, compound objects are less likely to be organized into a single object by bottom--up grouping processes. Our results indicate that while search rates in a sparse display may be determined by the number of objects, search rates in clutter are also affected by the number of object parts.

Adult↗