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.
