AQA Specification B Unit 2 Illusions

Depth cues such as linear perspective or height in plane are used itentionally to cause us to engage in constancy scaling (we naturally percieve 2D as 3D) many distortion ilusions cause uus to use size constancy scaling.

As the fins give linear perspective, the line on the right is unconciously percieved as being closer to us whilst the line on the left is percieved as being further away. the most famous interpretation of this illusion is the 'Carpented world hypothesis'- whilst the line on the left is percieved as the inside corner of a room streching further away from us, line b is percieved as the outside corner of a building which is closer to us.

The viewer tends to percieve the top horizontal line as longer than the one below. This distortion effect occurs because there are two depth cues in the drawing that lead us to belive the top line is further away than the bottom one:

-linear perspective (diagonal line appear to converge, like railway lines)

-Height in horizontal pane (the top line is higher up in the drawing so it is interpretated as further away and the retinal image is seen as the same size so it must be bigger)

-we seem to percieve simple 2D drawing as 3D

-we use monocuar depth ces, such as linear perspective and height in plane to infer depth

-we size size constancy scaling to mentally enlarge objects that we believe to be further away from us