I

Illuminated manuscripts were created as objects of luxury during the medieval and Renaissance eras.

illusion form (drawing, figure, photo) that produces an erroneous perception. People are typically fooled into seeing AB as longer than CD, even though it is not. Called the MüllerLyer illusion, it is caused in all likelihood by the fact that people are accustomed to interpreting outwardextending arrowheads as increasing the length of lines and, vice versa, to interpreting inward-extending arrowheads as decreasing the length of lines. In cultures where such drawing techniques do not exist, it has been found that the illusion does not occur.