How Categorization Warps Perception People who see the lines on the right tend to overestimate the similarity of lines 1 and 3 and underestimate the similarity of lines 3 and 4. Simply labelling lines 1–3 Group A and lines 4–6 Group B causes the lines within a group to seem more similar to each other than they really are, and the lines in different groups to seem more different from each other than they really are.