Thematic roles as verb-specific concepts

Thematic roles are typically viewed as slot and filler mechanisms in which the slots are devoid of content, or the content is limited to a few syntactically relevant features. This traditional view excludes important knowledge that people possess about who tends to do what to whom in specific situations. Thus it was extended here by treating thematic roles as verb-specific, feature-based concepts. In Experiment 1, subjects produced features for agent and patient roles such as ''someone who is frightened''. Role/filler typicality ratings, in which subjects provided judgements for questions such as ''How common is it for a monster to frighten someone?'' (i.e. monster as an agent of frighten), were collected in Experiment 2A. In Experiment 2B, different subjects were presented with the role features from Experiment 1 and the typical agents and patients from Experiment 2A. They were asked to rate how central each of the role features was to the nominal concepts, and role/filler featural similarity was calculated from these ratings. Analogous to studies of object concepts, role/filler featural similarity predicted role/filler typicality, thus suggesting that thematic roles and nominal concepts are represented in similar forms. Experiment 3 was a self-paced reading study in which adjectival features were used to bias an initial noun concept towards being a good agent or patient of the past participle of a reduced relative clause (''The shrewd heartless/young naive gambler manipulated by the dealer had bid more than he could afford to lose''). Featural bias modulated ambiguity resolution. The present work, in conjunction with other recent results, suggests that thematic roles might best be viewed as verb-specific concepts, and that this conceptual/world knowledge is computed and used immediately in on-line language processing. Results are discussed in relation to other recent treatments of thematic roles as well as constraint-based and garden path models.