Characterizing the nature of visual conscious access: the distinction between features and locations.

The difference between the roles of features and locations has been a central topic in the theoretical debates on visual attention. A recent theory proposed that momentary visual awareness is limited to one Boolean map, that is the linkage of one feature per dimension with a set of locations (L. Huang & H. Pashler, 2007). This theory predicts that: (a) access to the features of a set of objects is inefficient whereas access to their locations is efficient; (b) shuffling the locations of objects disrupts access to their features whereas shuffling the features of objects has little impact on access to their locations. Both of these predictions were confirmed in Experiments 1 and 2. Experiments 3 and 4 showed that this feature/location distinction remains when the task involves the detection of changes to old objects rather than the coding of new objects. Experiments 5 and 6 showed that, in a pre-specified set, one missing location can be readily detected, but detecting one missing color is difficult. Taken together, multiple locations seem to be accessed and represented together as a holistic pattern, but features have to be handled as separate labels, one at a time, and do not constitute a pattern in featural space.