Is dual-task performance necessarily impaired in space?

Recent single-subject experiments in space have reported impaired dual-task performance that could result from either a direct effect of microgravity on the central nervous system or from the multistressor environment. We sou ght to distinguish between these hypotheses using 6 astronauts in the 16-da y NASA Neurolab mission, testing them at intervals with a dual task consist ing of primary pursuit tracking without vision of the hand and secondary re action time (RT). The participants were highly trained, instructed to maint ain a fixed attention strategy, and restrained in the apparatus. The result s showed that absolute and variable tracking error, as well as correct RT a nd the standard deviation of RT, were unimpaired. However, RT errors became more variable. an effect attributed to a decrease in strategic control. We conclude that the impairments observed in previous dual-task space experim ents can be attributed to stressors rather than to microgravity and that pe rformance deficits are probably not a necessary concomitant of space flight if attention is paid to task design and astronaut training.