Ethological experiments on human orientation behavior within a three-dimensional space--in microgravity

In weightlessness situation the subject has to realize domestic and professional tasks comparable to those performed under normal gravity, whereas the "body tool" available to him has been placed in new conditions which require significant behavioral changes. The loss of weight, the disappearance or modification of some ideothetic and allothetic cues, notably the absence of gravity for the body's referential verticality have the most obvious effect of diversifying the astronaut's orientations. The vertical position is thus no longer the only one possible. This means that in order to efficiently accomplish his tasks, the subject has to invent new motor strategies which transform the quality of displacements and manipulations on the basis of the new orientation possibilities in a three-dimensional space. The previous ethological studies have dealt, in a global way, with the astronaut's motor behavior in microgravity, revealed according to an exhaustive quantitative description of the behavioral manifestions as a whole in terms of movement, posture and orientation. We now propose focusing more specifically on his spatial behavior in a three-dimensional space in microgravity. Such a situation is an exceptional experimental paradigm since at every moment, the relationships of the body referential to the surrounding space are infinitely variable: a man in space has to extract, process or use spatial information between the referentials of his moving body in all directions of the three-dimensional space and the fixed referentials of the physical environment of the space habitat. Furthermore, in the temporal dynamics, the previous ethological results showed that the behavioral events change according to the duration of the space mission, passing through different adaptative stages from a large behavioral diversity to complete behavioral reorganization. On the first day of his space mission the astronaut has however acquired experience of microgravity through his training, simulated on the ground and realized in parabolic flights. Some immediate adaptative processes are already present. As a result, the subject's experience of such a situation has to be emphasized from the initial moments of adaptation to microgravity. We thus postulate that the subject, through his orientation behavior in a three-dimensional space, according to his experience and over time, would elaborate a new representation of the space, as part of the whole adaptative process to this new environment. In order to verify such hypotheses, the present study will propose three levels of observation, i.e. three experiments in conditions of orbital flight, parabolic flight, visual simulation.