Abstract
We perceive an object, e.g., a frog jumping around, as a continuous entity, even if the object temporarily disappears behind other objects on its path. In order to solve this correspondence problem our visual system has to connect the right instances of an image across space and time. It has been suggested that this process can depend on image-based information, i.e., the retinal size of an object, as well as on object-based information, i.e., the perceived size of an object. Manipulating object-based information, however, often leads to changes of image-based information, e.g., luminance contrast, as well. Our aim was to clearly distinguish between these two levels by manipulating the temporal history of objects without changing the objects themselves. We used a Ternus display, an ambiguous apparent motion display. Depending on how correspondence is solved, the Ternus elements are perceived either as moving together (group motion) or as one element jumping across two others (element motion). We manipulated the temporal history of the Ternus elements by showing a short movie prior to presenting the Ternus display itself. In the movie, the Ternus elements either moved together along the same trajectory (common history) or separately (separate history), in order to manipulate how much the elements were perceived as connected to each other. If the object-based information about the history of the Ternus elements plays a role for establishing correspondence, we expected more group motion percepts in the common compared to the separate history condition. We found the expected result, but only if the motion in the movie was similar to the Ternus motion. In addition, this history effect could be generalized to another type of history, i.e. synchronized and desynchronized luminance changes. Our findings confirm that object-based information can influence object correspondence strengthening the evidence in favor of an object-based correspondence mechanism.
Acknowledgement: This study was supported by the German Research Foundation (HE 7543/1-1).