Intrasaccadic orientation changes in stationary and moving objects

V. Gysen, C. Lamote

Laboratory of Experimental Psychology, Department of Psychology, University of Leuven, Tiensestraat 102, B-3000 Leuven, Belgium (e-mail:gysen.veerle@psy.kuleuven.ac.be)

An experiment is conducted to examine the detection rate of intrasaccadic orientation changes for stationary and moving objects. The influence of organisational factors present in the scene is investigated. Previous research indicates a quite high detection rate of intrasaccadic changes in the orientation of a stationary object. The detection of those changes for a moving object (rotating) were rather poor (Verfaillie, K., De Troy, A. and Van Rensbergen, J., 1994, Journal of Experimental Psychology: Learning, Memory, and Cognition, 20: 649-670). Whether this means that orientation information extraction is less exact for moving objects then for stationary objects remains unclear. Its importance can depend upon the kind of movement in which the object is involved or even the kind of orientation change. In other words, the organisational factor in a scene can (as in position change detection) be important for orientation change detection. The stimulus situation used in the experiment shows one object moving horizontally towards another (stationary) object. By manipulating the combinations of the two possible orientations for the stationary and moving object, different situations (organisations of the scene) are created. In some of these situations, no orientation change takes place. In others, the orientation changes concern the moving object and result in a 'turning' of the moving object towards or away from the stationary object. In the last type of situations orientation changes of the stationary object result in a 'turning' away from or a 'turning' towards the moving object. The influence of the status of the object (stationary or moving) and the kind of orientation change on detection of orientation changes made during eye movements, is examined. The results are discussed in the scope of theories on transsaccadic memory.