A device for selectively detecting in real time a moving object progressing on a path in a multidimensional space, the device comprising first means determining an efficiency, corresponding to the ratio of net displacement to total distance travelled, and for selecting moving objects on the basis of this ratio. To account for objects making half turns in an otherwise efficient path, from the data constituted by the measurements of displacements of the moving object, an average of the efficiency of motion is used. The device is useful, for example, for real-time image sequence processing in conjunction with the tracking of moving objects.