Active control has further a positive effect on recognition tasks. Simons and Wang (1998) compared active to passive viewpoint changes. Familiar objects (like a brush or a mug) were presented on a circular table. Subjects had to remember the position of all objects. Two set of trials were compared. In the first set, the subjects walked to another viewing position, and in the second set, they were either passively moved (in a wheelchair) or the table was rotated (the change of the retinal image was the same in all conditions). In the active condition, changes were recognized easier. In a different study, novel 3D objects were presented on a computer screen (Harman et al., 1999). In the training block, subjects could either explore the objects by rotating them with a trackball, or they passively observed the rotated objects. Later, in the test block, actively explored objects could be easier recognized than passively observed ones (in an `old/new' discrimination task). The advantage of active exploration over passive observation was further found in virtual reality studies (James et al., 2002).