Perceptual Illusions in Imagery

Investigated the phenomenon of optical illusions. The authors argue that a mental image should not be particularly sensitive to variables which are critical in producing an optical illusion, i.e., variables affecting the early phases of information processing and field global effects. It is hypothesized that an optical illusion will be present in a perception condition but not in an equivalent imagery condition. Two experiments were conducted using the Ebbinghaus illusion and the Ponzo illusion. In Exp 1, 25 19–25 yr olds participated in perception and imagery conditions. In Exp 2, 39 20–24 yr olds were assigned to 1 of 2 experimental groups or a control group. The 1st experimental group, the perception condition was the same as in Exp 1. In the 2nd experimental group, the perception condition was the same as in the 1st group, with changes in the instructions for the imagery condition. The control group was included to see how Ss rated the size of the stimuli independently of the inducing elements. Results confirmed the hypothesis and demonstrated that there are asymmetries between perception and imagery and that such differences mainly concern specific perceptual processes that differ from those involved in the generation of a mental image. (