A test of the relational hypothesis of perceived size.

a size-induction effect. Although this effect is not large when the stimuli are presented in a well-structured visual field, it increases if nothing is visible except the two lines and two frames--presumably because the additional portions of the field provide a more inclusive surround that limits the induction effects of the individual frames (Rock and Ebenholtz, 1959). A phenomenon similar to size induction occurs in the perception of motion. Brown (1965) was able to summarize the results from a series of experiments on motion perception under the concept of the transposition principle. He found that the apparent velocity of a small moving object within a frame depends on the size of the frame and that if all the dimensions of the object and frame are multiplied by a constant (transposed), the physical velocity of the moving object must be multiplied by approximately the same constant in order for the perceived velocity to remain unchanged. Assuming similarity of the processes underlying the perception of size and velocity (Rock, Hill, and Fineman, 1968), the transposition principle can be applied to the perception of both size and velocity, to determine the theoretical values the induction effects would approach if no contrary factors were present. In size induction, for example, if only the induction effect were present, a 1-in. line in a 2-in.