ABSTRACT
The topic of this chapter is naturalistic action, by which we mean movement in the service of commonplace, practical goals like food preparation and consumption. Naturalistic action involves sequences ofmovements that areweil established through practice, for example, cutting food with fork and knife, spearing food onto the fork, and bringing the fork to the mouth. As such, it represents a class of skilled action. lt is also movement carried out with and upon objects 1, and hence it utilises knowledge about the function and usage of objects (e.g. the spearing function of the fork). Finally, since naturalistic action is organised by goal hierarchies that structure behaviour over reasonably long time frames, it requires planning, attention, and working memory-functions served, at least in part, by the frontallobes. Given these attributes, it is somewhat surprising that naturalistic action and naturalistic action disorders do not feature prominently in neuropsychological theories of skilled action, conceptual (semantic) memory, or frontallobe functions. 2
There are several probable reasons why naturalistic action has attracted so little attention in the neuropsychological literature. Traditionally, the neuro-
psychological examination has taken place at the bedside and in the laboratory, neither of which provides adequate opportunity to assess naturalistic action. Perhaps because of this, naturalistic action disorders are unlikely to come to the attention of investigators unless they are dramatic; and dramatic breakdown of naturalistic action is thought to occur only in conditions in which the darnage to cerebral structures is diffuse andlor extensive (e.g. late stage Alzheimer's disease; severe traumatic brain injury). Thus, there is widespread beliefthat focal lesions do not seriously disrupt naturalistic action, especially when performed in the natural setting. But if, as we suggest, naturalistic action draws on such functions as sequential movement control, semantic memory, and goal-based planning, it might be expected that focallesions compromising any one of these functions should have identifiable effects on performance. Throughout this chapter, we will be examining the small body of sturlies that bears on this question. But for now, Iet us assume that it is true that focal cerebrallesions do not seriously impact naturalistic action performed in context, and Iet us ask why this should be so.
