Abstract
In this report, we made cable-stayed bridges the simple figures and measured the illusional amount of the height of the tower about three kinds of shape (harp system, fan system, star system)of the cable.As a result of the experiment, thefigures with the cable overestimated the height of the tower in comparison with the figures which the cable was not in.It found out the next things about the illusional amount harp system was the biggest, and star system was the smallest.Next, the figures which didn't project was compared with the figures that the tip of the tower projected in the top from the top end of thc cable.we got the interesting result that the illusional amount was different at each case.Subjects overestimated the tower, about the figures that the tip of the tower didn't project from the top end of the cable greatly.
