The spread of attention and learning in feature search: effects of target distribution and task difficulty

We examined the roles of two determinants of spatial attention in governing the spread of perceptual learning, namely, stimulus location distribution and task difficulty. Subjects were trained on detection of a target element with an odd orientation imbedded in an array of light bars with otherwise uniform orientation. To assess the effects of target distribution on attent ion and learning, target positions were distributed so that attention was a llocated not only to the target positions themselves, but also to intermedi ate positions where the target was not presented. Target detection performa nce substantially improved and improvement spread to match the induced wind ow of spatial attention rather than only the actual target locations. To as sess the effect of task difficulty on the spread of attention and learning, the target-distracter orientation difference and the time interval availab le for processing were manipulated. In addition, we compared performance of subjects with more versus with less detection difficulty. A consistent pat tern emerged: When the task becomes more difficult, the window of attention shrinks, and learning becomes more localized. We conclude that task-specif ic spatial attention is both necessary and sufficient to induce learning. T he spread of spatial attention, and thus of learning, is determined by the integrated effects of target distribution and task difficulty. We propose a theoretical framework whereby these factors combine to determine the corti cal level of the focus of attention, which in turn enables learning modific ations. (C) 2000 Elsevier Science Ltd. All rights reserved.