Disorganisation of behaviour after frontal lobe damage

Abstract This paper presents a theory of the disorganisation in activity that can follow frontal lobe damage. This disorganisation is characterised by fragmented sequences of action, relevant parts being omitted and irrelevant parts introduced. Following Bianchi (1922) and Luria (1966), a defect is proposed in the role of purpose: control of action by its intended result. Concepts from human and machine problem solving are used to elaborate this idea. An attempt is then made to show which aspects of frontal impairment are relevant to assessment of the theory. Of most importance are the generality of impairment—its appearance across the range of information-processing domains and task components—and in particular the detailed behaviour surrounding failure to achieve known goals. These, I suggest, should form the basis of a functional characterisation of the disorder. An important point is that the theoretical function proposed—search for a structure of action optimising achievement of listed goals—is only one factor influencing the organisation of behaviour. Another is the repetition of familiar sequences of action in familiar settings. This may correspond to the common idea of a distinction between two modes of processing, active/controlled and passive/automatic.