Abstract
In a normal change-detection task, observers should encode a study image, retain its representation for a time interval, retrieve this representation and compare it with a test image. Many studies indicate that attention is not necessary for retention of a representation, whereas it is essential for encoding and retrieving a representation (e.g., Hollingworth, 2003). In normal change-detection tasks, however, multiple objects are presented within study and test images, making it difficult to examine sustained attention on a single target object. Therefore, the role of sustained attention in change-detection tasks remains unclear. To examine this issue, we conducted an object orientation change-detection task, manipulating an object location between study and test displays (same or different location). Use of a single object should ensure focal attention to that object. In Experiment 1, a study image was presented for 500-ms, and ISI differed (200-ms or 1000-ms). We hypothesized that location shifts require corresponding shifts in spatial attention to the new location, hence should interfere with change-detection. However, location shifts interfered with change-detection performance only in 200-ms condition. Further, in the same location condition, performance was higher in the 200-ms condition than in the 1000-ms condition. In Experiment 2, using a 200-ms ISI, we manipulated the SOA between study and test images (700-ms or 1500-ms) and object location. In this experiment, performance was better for the same (versus different) locations in both SOA conditions. These data are consistent with a suggestion that spatial attention is sustained for a short time interval (Nakashima & Yokosawa, 2010, VSS); they further imply that this time interval is determined by the ISI and not by the SOA. That is, focused attention on an object region is sustained over a subsequent short blank time interval and this facilitates change detection.