A common denominator can be found permeating thought disorder at various levels – the lack of executive planning and editing. With data available from aphasiology and neuropsychology, certain features of thought disorder can be reinterpreted as being consistent with dysfunction of the frontal lobe. It is hypothesised that thought disorder may reflect a dysfunction of the cortical–subcortical loops that project into the pre-frontal cortex. The hypothesis predicts that thought-disordered patients will have impaired performance on tests of frontal lobe function, regardless of diagnosis.