Dual-task performance on an interactive human/computer space shuttle flight experiment.

INTRODUCTION This paper details ground-based results of the Mental Workload and Performance Experiment (MWPE) which examines human performance for cognitive decision-making and eye-hand-coordinated motor tasks. MWPE is manifest on the International Microgravity Laboratory (IML-1) Space Shuttle Mission and is scheduled to fly in December of 1990. The MWPE protocol combines a Sternberg memory search with a Fitts' target acquisition resulting in a "Fittsberg" dual-task paradigm. The purpose of this study was to evaluate the serial execution theory underlying the Fittsberg dual-task paradigm. METHODS A total of nineteen subjects performed two experimental test batteries. Unusual body dynamics were imposed on subjects in order to assess altered environment performance. In the first test battery, subjects performed experiments in either the upright postural orientation or the supine (recumbent) postural orientation. During the second test battery, an altered environment was electronically created by introducing a first-order lag characteristic between the graphic input device and the computer. Performance and workload were evaluated by reaction time, movement time, and subjective rating measurements for the dual-task paradigm. RESULTS The major contributors to reaction and movement times are as predicted by Sternberg and Fitts, however, there are many other influences not accounted for by the classical models. For MWPE, interdependence among the memory set size and index of difficulty experimental variables is in conflict with the serial execution assumption of the Fittsberg dual-task paradigm. CONCLUSIONS When interaction among variables exists, the dual-task paradigm can not simply be modeled as a Sternberg memory task plus a Fitts target acquisition, rather, new performance metrics for the memory search and target acquisition tasks require that all the significant variables in the MWPE protocol be modeled. The interdependence among variables hints that the operator incorporates some degree of parallel processing rather than exclusively performing in a serial manner.