Abstract
Abstract: In previous experiments we tested detection of intrasaccadic position changes for stationary and translating objects. Both types of objects were present on the screen and one of the objects could be displaced intrasaccadically. Detection was higher for displacements of translating objects than for displacements of stationary objects. Two possible explanations were investigated. One possibility is that the translating object was coded with reference to the stationary object. This was examined by comparing detection of intrasaccadic displacements of an isolated object vs. displacements of an object translating toward another. This manipulation had no strong effect. A second possible explanation is a mechanism with high temporal and spatial resolution optimally adapted to keep track of translating objects even across saccades. We hypothesized that the immediate postsaccadic presence of the translating object was crucial for adequate sampling of spatial information and thus for high detection. This account was tested by introducing a postsaccadic blank (objects were not visible for 60 or 220 ms after the saccade) for stationary and translating objects. The data showed that blanking (compared with no blanking) increased detection of position changes for static objects (conform with Deubel, Schneider, & Bridgeman, 1996), whereas detection of displacements for translating objects deteriorated. This suggests that for transsaccadic perception of spatial information different mechanisms are at work for stationary and moving objects. Especially for a translating object, fast postsaccadic access to object or motion information seems vital for accurate detection of changes in its motion path.
This research is supported by Concerted Research Effort Convention GOA 98/01 of the Research Fund K. U. Leuven, and the Belgian Programme on Interuniversity Poles of Attraction Contract P4/19.