When an observer moves through the environment, moving images form on his or her retinae. The visual perception of self-motion is provided by expanding or contracting visual fields projected on the retina. Gibson (1950) called this particular motion, originated by the observer’s own navigation, “Optic Flow”. He noted that when an observer moves forward, fixating his or her final destination, the expanding visual field seems to originate from a specific point and he named this point “Focus of Expansion” (FOE). In everyday life, self-motion perception is more complicated, because eye and vestibular movements almost always occur together with the optic flow. For example, during locomotion, we experience retinal flow, composed of the translational and rotational components of eye, head and body movements, and optic flow (Lappe et al., 1999). Although all the self–motion perception mechanisms are not clear yet, it seems that the visual system analyzes the visual component, i.e. the optic flow, first and then it combines the optic flow with the other retinal and extraretinal signals in order to construct a dynamic map of extrapersonal space suitable for self–motion guidance (Regan & Beverley, 1982; Warren & Hannon, 1990; Lappe et al., 1999).