Eying the eyes in social scenes: Diminished importance of social attention in simultanagnosia

Simultanagnosia is a disorder of visual attention that results from bilateral lesions to the parieto-occipital junction. These patients have difficulty seeing more than one object at a time. We previously reported that simultanagnosics allocate abnormally few fixations to the eyes of people in social scenes. Given that healthy individuals look at the eyes of others to infer people's attentional states, this finding might reflect that a) for simultanagnosics the attentional states of others are not a high priority or, b) these patients are unable to use the eyes to infer the attention of others. To distinguish between these two alternatives we monitored the eye movements of simultanagnosic patient GB, and healthy controls, while they 1) described social scenes, or, 2) inferred the attention of people in the scenes. Consistent with past work, healthy individuals tended to look at the eyes of others in both conditions, but significantly more so when explicitly inferring the attentional states of the people depicted. GB fixated the eye regions far less than controls while describing social scenes, but performed similar to controls when explicitly asked to infer attentional states. Thus, like healthy subjects, GB shares a top-down understanding that the eyes are an important source of information for the attentional states of others. However, when deriving scene information, this attentional information is not normally prioritized by simultanagnosic patients to the same degree as it is by healthy individuals. This indicates that when multiple objects in a scene are not available concurrently a key social attention cue – eye gaze – is not used, despite the fact that knowledge of the value of this cue exists.