Many studies have suggested that visually-guided action is largely immune to the effects of several pictorial illusions that strongly influence perceptual judgments. The judgments in these experiments, however, have usually involved comparisons of multiple elements within a display, whereas the visually-guided actions have typically involved a pincer grip directed to only one display element. The three experiments presented here assess the influence of this confound on the perception versus action illusion dissociation. In general, the studies suggest (a) that the confound affects perceptual judgment but not grasping or manual estimation, and (b) that difficult visuomotor tasks are more affected by the @entity10582 than easier tasks. In Experiment 1, @entity1 reached for or made judgments about plastic disks placed in the center of the @entity10582 display. Some @entity1 reached for or made judgments about only the disk on the right, whereas others reached for or judged both disks simultaneously. A large effect of the illusion was found for grasping and comparative judgment, but not for manual estimation or metric judgment. In Experiment 2, the disks were elevated slightly to make gripping the targets easier, and the effects of the illusion on grasping were greatly reduced. For Experiment 3, @entity1 performed the manual estimation task while the hands were placed in view, on the surface of the table, and the effects of the illusion were significantly increased. Taken together, the experiments indicate that task difficulty and hand visibility affect whether a task will be influenced by pictorial illusions or not. One- and two-handed grasping seem to be affected approximately equally.

Effects of the XXXX on different behaviors: one- and two-handed grasping; one- and two-handed manual estimation; metric and comparative judgment.

@entity1 :: ('9606', 'Species') :: ['participants'] @entity10582 :: ('MESH:D007088', 'Disease') :: ['Ebbinghaus illusion']
@entity10582 :: (MESH:D007088,Disease) :: ['Ebbinghaus illusion']
