Birds of a feather flock together: Similarity judgments with semantically rich stimuli

The structural-alignment approach to similarity posits a principled distinction between object attributes and relations between objects. We examined whether this assumption holds for nonarbitrary combinations of interrelated objects. Subjects judged similarity between simple statements in which the nouns (denoting attributes) and verbs (denoting relations) were semantically interdependent. We found that semantic dependencies affected similarity judgments both by inducing inferences about the abstract combined meaning of the statements and by changing the process by which subjects arrived at their judgments. When the paired statements had matching verbs (e.g., "The carpenter fixed the chair" and "The electrician fixed the radio"), subjects compared the combined meanings of the statements (e.g., "Similar because both are professionals doing their job"). These results are consistent with the logic of structural alignment. However, when the paired statements had matching nouns (e.g., "The carpenter fixed the chair" and "The carpenter sat on the chair"), very often subjects integrated the combined meanings of the statements (e.g., "Similar because he sat on the chair to see whether he fixed it well"). These results defy every existing account of similarity. We discuss the prevalence and systematicity of such processing replacements and the need for incorporating them into similarity-based accounts of cognition.