The spatial profile of visual attention in mental curve tracing

In a curve-tracing task, subjects have to judge whether items are located o n a single, continuous curve. Spatially separate segments of such a curve a re related to each other through grouping criteria, like collinearity and c onnectedness. These grouping cues need to be exploited during curve tracing , but it is still an open issue how grouping of contour segments is achieve d by the visual system. Many contemporary theories of visual perception ass ume that grouping operations are carried out pre-attentively, with unlimite d capacity. The present study examines this assumption by investigating the involvement of attention in curve tracing. The results show that attention is directed to contour segments that need to be grouped together. The dist ribution of attention is guided by grouping criteria, such as connectedness . Apparently, attention is required to group spatially separate contour seg ments into a coherent representation of a curve. (C) 2001 Elsevier Science Ltd. All rights reserved.