ABSTRACT
In order to perceive an approaching object, many cues are available, classically subdivided in pictorial depth cues (PDC) and motion-produced cues (MPC). The PDC may be used in an indirect access method to time-to-contact (e.g., Cavallo & Laurent, 1988). For instance, distance information can be based on the size-distance invariance hypothesis. In contrast, MPC (mainly studied by the ecological approach, see Gibson, 1979), are directly available in the optic array. For instance the optical variable tau (Lee, 1976) is information about the time remaining before contact.
