THE HORIZONTAL-VERTICAL ILLUSION IN PLANE GEOMETRIC FIGURES,

The purpose of the experiment was to determine whether the classical statement of the horizontal-vertical illusion which states that the vertical dimension is seen as perceptually longer than the horizontal dimension is descriptive of judgments of plane geometric figures. The results did not wholly agree with the classical statement of the horizontal-vertical illusion. The data from the square-rectangle series suggest the operation of two distinct differential effects. First, it would seem that while the classical illusion exists in some figures, a nonclassical, or even no illusion, exists in other figures, and, therefore, the classical statement which says that the vertical dimension is perceptually lengthened does not hold, arbitrarily, for all figures. Each individual figure must be studied before any definite statement can be made about the illusory effects of that figure. Secondly, there is a difference in subjects as to whether they see the illusion or not. A square, for example, consistently looks like a vertical rectangle to some subjects and appears as a horizontal rectangle to others. Author