depth ambiguities. Without promoting the cues, their raw data (e.g., disparities and velocities) are in different units so that simple cue-combination strategies, such as averaging the depth estimates made using each cue, are impossible. When the missing parameters are the eye positions (vergence, gaze directions, and torsions), the promotion process is referred to as depth scaling. In particular, in central gaze, the raw sensory data for the cue (velocities, disparities, etc.) are scaled by (that is, multiplied by, or multiplied by the square of) an estimate of the fixation distance. To the extent that this scaling is done accurately, the result is depth constancy: perceived depth that is independent of changes in viewing conditions. In this hapter we will limit our discussion of cue promotion to the issue of scaling by the fixation distance. We review a number of ways in which depth scaling may be accomplished. Micha

The target article is based on the assumption that our senses' ultimate purpose is to provide us with perfect information about the outside world. We argue that it is often more important to have information quickly, than for it to be perfect. Consequently our nervous system processes different aspects of information about our surrounding as separately as possible. The separation is not between the senses, but between separate aspects of our surrounding. This results in inconsistencies between judgements, sometimes because different frames of reference are used. However, such inconsistencies are fundamental to the way the information is picked up, and therefore cannot be avoided with clearer instructions to the subjects. Since the target article deals with human interactions with the environment it is impossible to ignore the physiology involved. Once one considers the physiology it becomes evident that in practice there can be no `specification' of the kind described in the target a...

The interaction of the depth cues of binocular disparity and motion parallax could potentially be used by the visual system to recover an estimate of the viewing distance. The present study investigated whether an interaction of stereo and motion has e#ects that persist over time to influence the perception of shape from stereo when the motion information is removed. Static stereoscopic ellipsoids were presented following the presentation of rotating stereoscopic ellipsoids, which were located either at the same or a di#erent viewing distance. It was predicted that shape judgements for static stimuli would be better after presentation of a rotating stimulus at the same viewing distance, than after presentation of one at a different viewing distance. No such di#erence was found. It was concluded that an interaction between stereo and motion depth cues does not influence the perception of subsequently presented static objects.

Abstract not found