Reference patterns and the process of normalization

Two experiments investigated the effect of reference patterns on the normalization process that involves the visual code. In Experiment 1, the subjects had to classify assame ordifferent two simultaneously presented letters. The upper letter was always in the upright position, whereas the lower letter could take six different orientations and was enclosed in a congruent triangular frame. The results forsame responses showed reliable orientation-dependent effects which clearly implied an operation of normalization. In Experiment 2, the orientation of the upper letter and that of its frame varied orthogonally, whereas the lower letter was always presented within a congruent frame at six different orientations. The results showed that the normalization occurred with reference to the orientation of the upper letter, and that the congruent upper frame could speed up the comparison process only at certain orientations of the lower letter. It was concluded that the direction of normalization depends on the orientation of the upper letter, and that the effect of the frame is interpretable in terms of a display symmetry facilitation effect.