A Perceptual Cue-Based Mechanism for Automatic Assignment of Thematic Agent and Patient Roles

Understanding social events requires assigning the participating entities to roles such as agent and patient, a mental operation that is reportedly effortless. We investigated whether, in processing visual scenes, role assignment is accomplished automatically (i.e., when the task does not require it), based on visuospatial information, without requiring semantic or linguistic encoding of the stimuli. Human adults saw a series of images featuring the same male and female actors next to each other, one in an agentlike (more dynamic/leaning forward) and the other in a patientlike (static/less dynamic) posture. Participants indicated the side (left/right) of a target actor (i.e., the woman). From trial to trial, body postures changed, but the roles, defined by the type of posture, sometimes changed, sometimes not. We predicted that if participants spontaneously saw the actors as agent and patient, they should be slower to respond when roles switched from trial n - 1 to trial n, than when they stayed the same (role switch cost). Results confirmed this hypothesis (Experiments 1-3). A role switch cost was also found when roles were defined by another visual relational cue, the relative positioning (where one actor stands relative to another), but not when actors were presented in isolation (Experiments 4-6). These findings reveal a mechanism for automatic role assignment based on encoding of visual relational information in social (multiple-person) scenes. Since we found that roles in one trial affected the processing of the subsequent trial despite variations in postures and spatial relations, this mechanism must be one that assigns entities in a scene, to the abstract categories of agent and patient.