Switching Attention between the Local and Global Levels in Visual Objects

Previous studies with compound letters have not been able to dissociate in time the presentation of the global and local levels. Therefore, direct timing of attentional shifts between levels has not been possible, nor has the Hillyard sustained-selective attention paradigm been fully applied. Here we describe work with a new approach, rapid serial object transformation, which shows that shifts of attention from the local to the global level are faster than in the opposite direction in typical observers. The method also enables independent estimates of the neural responses to local and global aspects, and was used to show that selection of one hierarchal level modulates early occipital-temporal components with a shorter latency effect for responses to global letters. The use of the method for basic research in visual perception is discussed and preliminary work with autistic observers (who have longer local to global than global to local attentional shifts) illustrates the potential of the paradigm for studying psychopathology. ?? 2014 Elsevier Inc. All rights reserved.