Conditions characterised mainly by disturbances in behaviour have generally been considered to be poorly understood and of interest and relevance largely to behavioural scientists. However, problems such as cognitive decline, aggression, and affective disturbance are common and are present in conditions that come under the care of professionals across a range of disciplines. For instance, aggressive behaviours develop in circumstances ranging from personality disturbances arising in childhood to disturbances of brain tissue. Basal ganglia disorders and the dementias are both increasingly recognised as broad disease …