Muller Layer Illusion

To determine the extent of space error movement error and error in perception of length of a line.

The instrument consists of a stand with a wooden block. The wooden block on the front has a thick straight line with a fixed arrow and two movable arrow pointers of the same length. The arrows are made in such a way that they act as open ended or closed embedded arrows.
On the rear side of the block a wooden scale is embedded. A certain length of the line equal to the fixed line with the help of pointer. The error in perception is measured with the help of scale at the rear.