Date of Award
Master of Arts
Dr. Frank A. Fatzinger
Dr. E. J. Asher Jr.
Masters Thesis-Open Access
Experimenters have used the inverted "T" to illustrate the horizontal-vertical illusion for many years. This illusion is characterized by the subject perceiving the horizontal line as shorter than the vertical line.
Credit is usually given to Fick (1851) for being first to call attention to the discrepancy between horizontal and vertical estimates. He demonstrated this by visually noticing that a bright square on a dark background looks like an oblong object. Hicks (1906) stated that Oppel was the first person to actually investigate the horizontal-vertical illusion.
The classical theory generally states that an equal length vertical line in a "T" figure will be regarded as being longer than a horizontal line only because of the horizontal-vertical relationship. This theory stood unchallenged until Pan (1936) suggested a possible interaction between the horizontal-vertical illusion and the illusion produced by a single division of a line (bisected line illusion). Titchener (1901) found that a single division of a line tends to shorten its apparent length.
Boersma, Frederick J., "An Investigation of the Horizontal-Vertical Illusion" (1961). Masters Theses. 4484.