Automatic statistical processing of visual properties in simultanagnosia.

Previous research has suggested that, when operating in a distributed attention mode, the visual system automatically represents visual displays by their overall statistics, rather than their individual properties. Recent neuropsychological work shows partly preserved distributed attention in simultanagnosic patients, who are typically defined as only perceiving one object at a time. Here we assessed whether GK, a patient with simultanagnosia, shows averaging of stimulus properties when distributing his attention across a set of items. We manipulated different stimulus properties in two experiments: color shades and size. We found that, when GK was in a distributed mode of attention, he (incorrectly) identified the mean object from two classes of exemplars more than in a control condition, when only one exemplar class was present. Overall, this study suggests that automatic statistical processing of color and size is possible in simultanagnosia.