Cognitive estimation in neurological disorders.

The Cognitive Estimation Test (CET) was devised by Shallice & Evans (1978) in an attempt to quantify the tendency observed in some patients with frontal lobe lesions to produce bizarre estimates in response to questions to which people do not usually know exact answers (e.g. 'what is the height of a double-decker bus?'), despite performing normally on standard intelligence tests. In the present study, the CET performance of a large number of patients suffering from head injury, brain tumour, ruptured aneurysm (anterior communicating artery and other), multiple sclerosis, dementia, encephalitis, Korsakoff's syndrome and anxiety/depression were compared with CET scores from 150 healthy controls. Patients with Korsakoff syndrome demonstrated significantly impaired CET performance. A subgroup of patients with discrete frontal lesions was compared with a group with localized non-frontal lesions. No significant difference in CET performance was observed between anterior and posterior lesioned patients. The sensitivity of the CET to anterior brain dysfunction is called into question by the present findings.