A lateralized bias in mental imagery: evidence for representational pseudoneglect.

One hundred right-handed healthy individuals were asked to imagine a familiar scene (the Piazza del Duomo, Milan) from two opposite viewpoints and report what they could see. For elements that should be visible from the participants' viewpoint, more elements were reported from the left side of the image than from the right, irrespective of view. These results establish that there is a lateralized bias in reporting the details in mental images--representational pseudoneglect. This bias is in the opposite direction and significantly smaller than the bias seen in individuals with representational neglect following right hemisphere damage. Representational pseudoneglect appears analogous to perceptual pseudoneglect and the two may share an underlying mechanism. The results are interpreted as indicating that pseudo-representational neglect arises as the result of a bias in the allocation of attention to the imagined scene.