ABSTRACT
Learning to walk implies the sensory integration of visual, vestibular, proprioceptive, and cutaneous information about the environment and the position of the body in space. This sensory integration occurs within a stable reference frame on which movement control is based (Paillard, 1988). It has been suggested that the head could be a natural frame of reference for movement control in adults owing to the fact that it contains the visual and vestibular systems (Pozzo, Berthoz, & Lefort, 1990). Indeed, in adults, the head is stabilized in space during various locomotor tasks. This head stabilization, which is manifested in the low dispersion of head angular displacements, could be a means of ensuring clear vision (Grossman, Leigh, Abel, Lanska, & Thurston, 1988) and could facilitate the integration of vestibular information. In an ontogenetic study, Assaiante and Amblard (1993) showed that head angular displacements along the three axes were also minimized in children aged 3 to 8 years. The same authors also showed that no stabilization in the frontal plane, either relative to space or to the shoulders, appeared by the end of the fourth month of independent walking (IW) (Assaiante, Tomachot, & Aurenty, 1993).
