Newman, D.J., and Bussolari, S.R., "Dual-Task Performance on an Interactive Human/Computer Space Shuttle Flight Experiment", Biomed. Sci. Instrum., 1990; 26:213-25.

INTRODUCTION. This paper details ground-based re-sults of the Mental Workload and Performance Experiment (MWPE) which examines human performance for cognitive de-cision-making and eye-hand-coordinated motor tasks. MWPE is manifest on the International Microgravity Laboratory (IML-1) Space Shuttle Mission and is sched-uled to fly in January of 1992. 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 per-formed ex-periments in either the upright postural orienta-tion 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 sub-jective 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 classi-cal models. For MWPE, interdependence among the memory set size and index of difficulty experimen-tal vari-ables is in conflict with the serial execution as-sumption 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.

Key Words: Mental Workload and Performance Experiment (MWPE), microgravity, dual-task performance, human/computer interaction.