People reliably violate the triangle inequality in judging similarity.
China and Cuba are similar, Cuba and Puerto Rico are similar, but China and Puerto Rico are not similar. Similarity ratings depend on the order in which items are presented. These and other similarity judgments appear to be based on a dynamic system that includes contextual information, and which dynamically highlights and weights a set of dimensions for comparison. The highlighted dimensions are those that exhibit variability in the context. Similarity judgments are based on a mechanism that dynamically alters the importance of dimensions as a function of their variability.