Learning of role-governed and thematic categories

• We examined how actors in events are categorized based on common relations.
• Relational categorization from highly similar events required little support.
• However when events only shared abstract relations, categorization was difficult.
• Analogical comparison enabled categorization based on common abstract relations.

Natural categories are often based on intrinsic characteristics, such as shared features, but they can also be based on extrinsic relationships to items outside the categories. Examples of relational categories include items that share a thematic relation or items that share a common role. Five experiments used an artificial category learning paradigm to investigate whether people can learn role-governed and thematic categories without explicit instruction or linguistic support. Participants viewed film clips in which objects were engaged in similar actions and then were asked to group together objects that they believed were in the same category. Experiments 1 and 2 demonstrated that while people spontaneously grouped items using both role-governed and thematic relations, when forced to choose between the two, most preferred role-governed categories. In Experiment 3, category labels increased this preference. Experiment 4 found that people failed to group items based on more abstract role relations when the specific relations differed (e.g., objects that prevented different actions). However, Experiment 5 showed that people could identify them with the aid of comparison. We concluded that people can form role-governed categories even with minimal perceptual and linguistic cues.