The effect of gravity on human recognition of disoriented objects

The role of non-visual cues, and particularly of signals tied to the direction of gravity, in the mechanisms of recognition of disoriented objects is reviewed. In spite of a limited number of studies, object recognition does not seem dramatically altered by weightlessness and astronauts can adapt to this novel environment. Particularly, mental rotation strategy can still be used in weightlessness with dynamic parameters relatively unchanged. Similarly, spatial coordinate assignment can be performed adequately under different gravitational conditions. However, signals related to gravity direction seem to be integrated in the early stages of visual processing. Thus, performances in symmetry detection tasks and visual search tasks are influenced by the gravito-inertial conditions in which experience are done. Functional roles of such a multisensory convergence on cortical visual neurons, partly confirmed by neurophysiological studies, are proposed.