In the figure-ground pereception, when the brightness-difference between the figure and the ground is reduced to zero, the figure disappears. Only when a certain amount of brightness-difference is retained, can we perceive a figure against the ground. For convenience sake, we call this critical difference in brightness the “visual-perception-threshold” (V-P-T).
The following account is the summary of the results of an experiment conducted in an attempt to determine the effeet of form upon the V-P-T.
1. The V-P-T decreases with the increase in the size (area) of the figure. This means that an additional quality, area, in the object of perception plays an important rôle in the perception of form.
2. The V-P-T of a rectangle is dependent upon its length. Here, also, the effect of area is pvedominant.
3. With respect to the perception of circles, triangles and other forms, we find that the V-P-T's of triangles and rectangles are small as compared with those of circles. This indicates, so we think, that circle is not a dominant form as so frequently stated by psychologists to the contrary.
4. When an inducing stimulus is introduced in the neighborhood of the object of observation in such a way as to form a Gestalt with the latter, the effeet produced is the same as in the case of 4: The effect of area is greater than that of the Gestalt.