The development of automation and computerization in many work, driving, or supervision stations tends to favorise or try to maximalize the operator's visual functions, in his role of the supervisor who can intervene in the case of abnormal behavior of the overall man-machine system. The supervisor, or the pilot, then goes from an alert state to a state of intense activity, where the speed and efficiency of his reactions are essential, while he himself is perturbed by a considerable increase in his work load, due to the quantity of information he must process, or, again, to direct "agressions" he may be subjected to, such as accelerations or vibrations of the vehicle he is in.An important experimental set-up, comprising, in particular, a modular motion generator with six degrees of freedom (roll, pitch, yaw, Χ, Y, Z) and a mobile visual information support (crystal and LED displays, and various screens) enables us to reconstitute a variable mechanical and visual environment representative of driving or piloting conditions ; various capters: accelerometers, ocubmeters (LETI, NAC Eye Marker), and joysticks, allow us to obtain the input and output variables, as well as those pertaining to the perturbations of the man-machine system under study. A synthesis of the results obtained leads to a model of the human operator's behavior when acquiring visual information while being perturbed by very low frequency vibrations, which subsists beyond the filtering devices.This model integrates the phenomena of visio-vestibulary interactions, as well as certain theories on information concerning the pilot's work load.Thus, a criterion of manual response time reveals that a rolling motion is the last perturbing, while the deterioration in performance, due to a pitching rotation is greater than that induced by yawing motion.Furthermore, in the range of less-than-one-hertz frequencies studied the frequency of 0, 6 Hertz seems to be a "threshold" from which the perturbing effects are more and more intense.The means by which the vehicle's vibrations are transmitted to the driver and the law of relative displacement between the operator's eyes and the visual information's support he is observing also turn out to be very important. These results are connected with the phenomena of oculo-vestibulary interactions revealed by measuring the operator's eye movements, and by complex experiments using several axes of perturbation simultaneously.The modelization of the phenomena observed allows one to consider, in an ergonomie perspective, the proposal of a "feedback" tending to modify, in real time, certain parameters, so as to optimize the performances of the overall man-machine system.