The whole section is based on the paper written by Kanizsa to refute Musatti’s thesis on the impossibility of running a crucial experiment on the role of past experience in perceptual organization. Kanizsa demonstrates that in various situations perception violates expectations based on acquired knowledge. The umbrella pole goes behind the girls’s hair exploits the so-called “Petter’s rule”, the tendency to see thinner zones behind thicker zones, when local information on the stratification direction is lacking. In the Little church line iteration masks a familiar shape. In E a letter is perceived only in the canonical orientation. Moltitumulinuovi and Nume illustrate the power of mirror masking: unusual forms, supported by closure, symmetry, and continuity of direction, prevail over well-known letters and words.
When the mechanical animation is observed (preferentially by a single eye) from a distance of at least four meters, the little man does not run, but rather hops, as if the back leg were hitting the other. Feet seem to bounce one against the other. By getting closer to the device, instead, one can see the actual crossing of legs. Curiously, our past experience with human figures that move forward by walking or running does not prevail over the perceptual tendency to avoid the crossing of kinematic trajectories.