Date of Award


Degree Name

Master of Arts



First Advisor

Frank A. Fatzinger

Second Advisor

E. J. Asher Jr.

Third Advisor

Stanley Kuffel

Access Setting

Masters Thesis-Open Access


The vertical-horizontal illusion has been the object of experimental study for many years. The first man to investigate the vertical-horizontal illusion was probably Oppel in 1854. Since the time of Oppel's first experiment, many theories have been advanced in an attempt to explain what causes this illusion to occur in our perception of connected vertical-horizontal lines. The primary theory that is most widely accepted states that the vertical line in the "T" illusion will be judged longer because of the vertical-horizontal relationship.

Pan (1934) suggested that the "T" figure illusion was not due entirely to the interaction of the vertical and horizontal line, but rather to the perculiar characteristics of the figure itself. He found less illusion present in vertical-horizontal lines when they did not form the "T" figure. In support of this theory Finger and Spelt (1947) found evidence that the vertical-horizontal illusion present in the inverted "T" figure was the result of the interaction of two separate illusions, i.e., overestimation of the vertical line and overestimation of the dividing line. Fatzinger (1951) stated that the bisected line and the vertical-horizontal position of the lines are only minor contributors to the total "T" illusion. He was able to determine, by rotating the "T" figure, that position of the "T" had little effect on the amount of illusion present. This finding did not support the primary theory of vertical-horizontal line relationships. Rather, he suggests that the total configuration of the "T" is the major determinant of the vertical-horizontal illusion found in that figure.

Included in

Psychology Commons