The visual space sense.

At the conclusion of this discussion it is important to keep in mind the influences of all the complex processes involved in visual spatial localization, among which stereopsis is only one. The various factors and cues for this spatial localization interact with, complement, reinforce, and perhaps even inhibit one another, depending upon the varying visual surroundings of the moment and upon the physiologic perfection of the visual apparatus. In one's daily work probably no single factor or group of factors dominates at all times. "Any one who knows how pliable our spatial visual perceptions are under the influence of various conditions of observation and under the influence of past experience, taken into account consciously or unconsciously, should not be surprised at the multiplicity of results of observations on different objects and with different observers" (see 18).