Multiple task demands in action disorganization syndrome

Abstract

We present novel evidence for specific, disruptive effects of multi-step task demands on the production of everyday life tasks in two patients with Action Disorganization Syndrome (ADS). Experiment 1 demonstrated that the patients were impaired at carrying out everyday life tasks but improved when they instructed the examiner to perform the tasks. Experiments 2 and 3 showed that the patients improved in their own performance when the demands were reduced – by eliminating the need to use their own task schema (Experiment 2) and by reducing the need for error monitoring (Experiment 3). Experiment 4 reduced sequential effects in task performance further by having patients perform the same individual actions as before but now out of the task context. The data indicate that ADS patients are vulnerable to multiple demands made during the performance of everyday life tasks and show abnormal, disruptive effects of three specific factors: (i) using a self-driven schema, (ii) error monitoring and (iii) the activation of prior actions from the same task. The implications for understanding ADS are discussed.

Keywords:

• Task demands
• Action schema
• Action disorganization syndrome
• Everyday action

ACKNOWLEDGEMENTS

This work was conducted in partial fulfilment of a PhD in Psychology from the University of Birmingham (Morady) and it was supported by grants from the MRC and the Stroke Association to the second author. We thank FK and BL for their kind participation.

Notes

¹A similar idea has been proposed by Botvinick and Plaut (2004), though they use a recurrent neural network rather than a competitive queuing mechanism to generate the sequential production of action.