The Principle of Similarity

Objects that are similar to one another, and that share similar characteristics, are perceived as belonging to a single group. This grouping happens purely on the basis of shared visual properties, even in cases where every individual item is spaced perfectly evenly (so that the principle of proximity plays no role at all). For instance, when small circles and squares of matching size are arranged so that they are evenly spaced both horizontally and vertically throughout a display, we still tend to perceive alternating vertical columns of "circles only" and "squares only" -- simply because items sharing the same s …