Mental transformation in a visual recognition task.

Rectangular geometrical patterns with equal number of lines, identical relations between their vertical and horizontal components, identical angles, line crossing knots and free ends of lines were presented tachistoscopically to human subjects with a restricted recognition time caused by backward masking. Symmetrical linear transformation with respect to the Y or X axes and rotations of the patterns were performed and the correctness of their reproduction was measured in psychophysical experiments. A mental pattern transformation was a fast operation (under 100 ms) not directly linked to a graphic or a verbal expression of the results of reproduction. Mental transformation is probably determined by the recognition process. Symmetrical transformations are easier than rotational, whereas the most difficult is a detection of a pattern differing in its form from those considered within a predetermined group of samples.