Certain patterns confuse your eyes and brain, causing you to
misjudge the size of a circle, or the length of a line. Though
hundreds of optical illusions have been recorded and studied
over the last century, researchers still do not always agree
on why these patterns cause errors in perception. Scientists
are fascinated by illusions because, by figuring out how the
eye and brain perceive them, the normal workings of the visual
system can be better understood. As Purkinje, a noted 19th-century
Czech physiologist, put it: "Deceptions of the senses are the
truths of perception."
