ABSTRACT
The discrepancy between apparent depth and real depth is complex to define. Once we include how our subjective activity is related to the external events in time, the picture only gets more complicated. An object that looks straight in the air is half-immersed in water. As a result, it looks as if there is a bend or break in it where it crosses the border between the water and the air. One difference for most people between seeing the shape in the bent stick phenomenon is that it is not merely through the air. It is also seen through the water. This is a difference in medium and arguably less common. A final suggestion seems most plausible to author based on author’s own experience. There is no appearance of depth in cases of geometric-optical illusion. However, in the perceptual process, at some point, there is some kind of unconscious judgement of depth.
