toms typically seen in subjects with disease of the frontal lobe (Frith, 1992; Levin, 1984; Liddle, 1987; Pantelis et al., 1992; Weinberger, 1988; Winograd-Gurvich et al., 2006). Additionally, it has been shown that such negative symptoms are related to defective perfor- mance on neuropsychological tests sensitive to