The Reversing Cubes Illusion

On the left is the ancient and well known reversing cube illusion. It is pre-Christian in its origins. If you stare at the cubes for any period of time they will go through spontaneous reversals. One moment the top faces are top faces and the next they become bottom faces. The illusion depends upon depriving the viewer of the cues needed to make a valid judgement as to which way the cubes should be viewed.

Add a man to one of the faces as shown here on the right and the ambiguity immediately disappears because the viewer has been provided with a cue as to how to read the image.

It occurred to me that, just as the absence of cues provides an ambiguity, the presence of contradictory cues could do the same thing ........... and thus “The Terrace” was born.