These visual illusions include balls rolling uphill and people leaning farther than normally possible without falling down. Psychologists at Berkeley state that all of the misperceptions stem from the simple fact that the house is slanted at a 20 degree angle. Professor William Prinzmetal states, "When the perceiver's body also is tilted, the distorting impact on vision is greatly magnified- up to two or three times." Another point he makes is that distorted orientation causes other senses to fall back while one's visual senses become heightened. People standing at impossible angles and water flowing uphill are related to the angle at which the house sits.