It is well-known that our eyes typically fixate those objects in a scene, with which interactions are about to unfold. During manual interactions, our eyes usually anticipate the next subgoal and thus serve top-down, goal-driven information extraction requirements, probably driven by a schema-based task representation. On the other hand, motor control research concerning object manipulations has extensively demonstrated how grasping choices are often influenced by deeper considerations about the final goal of manual interactions. Here we show that also these deeper considerations are reflected in early eye fixation behavior, significantly before the hand makes contact with the object. In this study, subjects were asked to either pretend to drink out of the presented object or to hand it over to the experimenter. The objects were presented upright or upside down, thus affording a thumb-up (prone) or a thumb-down (supine) grasp. Eye fixation data show a clear anticipatory preference for the region where the index finger is going to be placed. Indeed, fixations highly correlate with the final index finger position, thus subserving the planning of the actual manual action. Moreover, eye fixations reveal several orders of manual planning: Fixation distributions do not only depend on the object orientation but also on the interaction task. These results suggest a fully embodied, bidirectional sensorimotor coupling of eye-hand coordination: The eyes help in planning and determining the actual manual object interaction, considering where to grasp the presented object in the light of the orientation and type of the presented object and the actual manual task to be accomplished with the object.

No abstract

No abstract

Our visual system establishes correspondence between objects and thus enables us to perceive an object, like a car on the road, as moving continuously. A central question regarding correspondence is whether our visual system uses relatively unprocessed image-based information or further processed object-based information to establish correspondence. While it has been shown that some object-based attributes, such as perceived lightness, can influence correspondence, manipulating object-based information typically involves at least minimal changes of image-based information as well, making it difficult to clearly distinguish between the two levels. To avoid this confound, we manipulated object-based information prior to the task in which we measured correspondence. We used 3-element Ternus displays to assess correspondence. These are ambiguous apparent-motion displays that, depending on how correspondence is solved, are perceived as either one element jumping across the others or as all three elements moving together as a group. We manipulated object-based information by presenting one of two object histories prior to the Ternus display. In one, they moved or changed luminance independently, and thus appeared independent from each other. In the other, the elements moved or changed their luminance all together and thus appeared grouped with each other. We found that the object history did influence how the Ternus displays were perceived, thereby confirming that object-based information alone can be used as a basis for establishing correspondence in line with object-based theories of correspondence.

The visual system constructs perceptions based on ambiguous information. For motion perception, the correspondence problem arises, i.e., the question of which object went where. We asked at which level of processing correspondence is solved – lower levels based on information that is directly available in the retinal input or higher levels based on information that has been abstracted beyond the input directly available at the retina? We used a Ponzo-like illusion to manipulate the perceived size and separations of elements in an ambiguous apparent motion display. Specifically, we presented Ternus displays – for which the type of motion that is perceived depends on how correspondence is resolved – at apparently different distances from the viewer using pictorial depth cues. We found that the perception of motion depended on the apparent depth of the displays, indicating that correspondence processes utilize information that is produced at higher-level processes.