 The aim of this project is to investigate whether alterations in sensory-motor performances during weightlessness are only of theoretical relevance, or indeed restrict the capacity of the participants. To find out, volunteers will monitor a complex realistic process by operation of buttons and switches in weightlessness. The task will mimic the control of vehicles, research equipment and industrial processes. Effects of weightlessness will be separated from effects induced by stress and those of motivation through evaluation of cortisol and manipulation of motivation. 