[Effects of rotation and distortion on perceptual priming]

We conducted two experiments to specify the properties of the representation underlying perceptual priming. We transformed a particular property of stimuli between study and test. We used novel stimuli to eliminate contamination by semantic memory. They were rotated by 0 degree, 90 degrees, or 180 degrees in Experiment 1 and were distorted horizontally in Experiment 2. These transformations were chosen for topological structures of stimuli to be kept unchanged. In Experiment 1 the priming effect of the rotated stimuli was smaller than that of the identical ones. The rotational angles had no effect. More surprisingly, the horizontally distorted stimuli showed the same amount of priming as the identical ones in Experiment 2. In contrast, recognition performance of the rotated or horizontally distorted stimuli was lower than that of the identical ones. Statistical independence between priming and recognition was found in both experiments. Thus, recognition was statistically and functionally independent of priming. These results suggest that the priming representation encodes both orientation-independent and orientation-dependent information, and that the global topological structure is critical for priming.