The study of cognitive and neuropsychological deficits constitutes an area in which research on schizotypals can be particularly useful. On the basis of the extensive neuroimaging and neuropsychological literature in schizophrenia, Bilder and Degreef proposed that the three affected systems include the periventricular region, the frontolimbic system, and the development of cerebral specialization, particularly the normal differentiation of the right and left hemispheres. Neuropsychological performance on tests measuring frontolimbic deficits and abnormalities of cerebral asymmetry has been studied extensively in schizotypy. Four types of neuropsychological tests examining different facets of cognitive inhibition have been utilized in studies of schizotypy. In order of increasing processing demands, these four include perceptual/sustained attention tasks, priming tasks, learning tasks, and conceptual inhibition tasks measuring perseveration. The evidence of hemispheric abnormalities in schizotypals has been presented in the context of three potential explanatory theories: left hemisphere deficit, left hemisphere overactivation, and interhemispheric transfer (IHT) abnormality.