An ecological approach to planning dysfunction: script execution.
Planning, which concerns many activities in everyday life, is a two-stage process. The first one predetermines a course of actions aimed at achieving some specific goals. It is founded on managerial knowledge or overlearned sequences of events and may be tested by script generation. The second stage entails monitoring and guiding the execution of the plan to a successful conclusion. It must take into account environmental contingencies and may be tested by script execution. If the frontal lobes intervene not only in managerial knowledge (Grafman, 1989) but also in binding the plan with contextual environment (Damasio, Tranel and Damasio, 1991; Shallice and Burgess, 1991), script execution would be more sensitive than script generation to planning deficits. To test this hypothesis, script execution and script generation were compared in 11 patients with a dysexecutive syndrome and 10 matched controls, using three scripts of daily life activities: (1) 'shopping for groceries'; (2) 'cooking'; (3) 'answering a letter and finding the way to post the reply'. Two way ANOVAs showed more errors in execution than in generation, more errors in patients than in controls, and a greater difference between execution and generation in patients than in controls. Furthermore, 'context neglect' and 'environmental adherence' were the two types of errors that best differentiated patients from controls. Finally, the total number of errors in execution correlated with the score on behavioral questionnaires answered by occupational therapists. These results confirm our hypothesis and suggest that script execution may be a valid ecological approach to estimate the severity of deficits in daily life activities.